Dermatopathology

The Diagnosis: Acquired Cutaneous Lymphangiectasia

Histopathology showed a cluster of widely ectatic, thin-walled lymphatic spaces immediately subjacent to the epidermis and flanked by an epidermal collarette (Figure, A). The vessels did not extend any further than the papillary dermis and were not accompanied by any notable inflammation (Figure, B). A single layer of bland endothelial cells lined each lymphatic space (Figure, C). A diagnosis of acquired cutaneous lymphangiectasia secondary to surgical and radiation treatment of breast cancer was made. Clinical monitoring was recommended, but no treatment was required unless symptoms arose. At 2-year follow-up, she continued to do well.

Acquired cutaneous lymphangiectasia is characterized by benign dilations of surface lymphatic vessels, likely resulting from disruption of the lymphatic system.¹ This finding most commonly occurs on the external genitalia following combined surgical and radiation treatment of malignancy, though in a minority of cases it is seen with surgical or radiation treatment alone.² Acquired cutaneous lymphangiectasia secondary to radical mastectomy for breast cancer was first reported in 1956 in a patient with persistent ipsilateral lymphadenopathy.³ The presentation in a patient with Cowden syndrome is rare. Cowden syndrome (also called PTEN hamartoma tumor syndrome) is a rare autosomal-dominant disorder caused by mutations in the tumor suppressor phosphatase and tensin homolog gene, PTEN. It is characterized by multiple hamartomas and substantially increased risk for breast, endometrial, and thyroid malignancy.⁴ In addition to breast cancer, our patient had a history of papillary thyroid carcinoma, cerebellar dysplastic gangliocytoma, and multiple cutaneous fibromas and angiolipomas.

A diagnosis of syringomas—benign tumors that arise from the intraepidermal aspect of eccrine sweat ducts— could be considered in the differential diagnosis. Cases of eruptive syringoma on the breast have been reported, but the biopsy would show a circumscribed proliferation of tadpole-shaped tubules comprised of secretory cells in a sclerotic stroma.5 Hidrocystomas are benign sweat gland cysts that present on the face, especially around the eyes, but rarely have been reported on the trunk, particularly the axillae.6 Although they clinically manifest as translucent papules, histopathology shows fluid-filled cysts lined by a layer of secretory columnar epithelium.7 Metastatic breast carcinoma was considered, given the patient’s history of breast cancer. Cutaneous metastases often are found on the chest wall but also can occur at distant sites. Histopathology can reveal various patterns, including islands of tumor cells with glandular formation or single files of cells infiltrating through dermal collagen.

Angiosarcoma also must be considered in the setting of any vasoformative proliferation arising on previously irradiated skin. Angiosarcomas can sometimes be well differentiated with paradoxically bland cytomorphology but characteristically have anastomosing vessels and infiltrative architecture, which were not identified in our patient. Other diagnostic features of angiosarcoma include endothelial nuclear atypia, multilayering, and mitoses. Radiation-associated angiosarcomas amplify MYC, a transcription factor that affects multiple aspects of the cell cycle and is an oncogene implicated in several different types of malignancy.⁸MYC immunohistochemistry testing should be performed whenever a vasoformative proliferation on irradiated skin is partially sampled or shows any features concerning for angiosarcoma. Lastly, the term postradiation atypical vascular lesion has been introduced to describe discrete papular proliferations that show close histopathologic overlap with lymphangioma/lymphatic malformations. In contrast, atypical vascular lesions show wedge-shaped intradermal growth that can cause diagnostic confusion with well-differentiated angiosarcoma. Unlike angiosarcomas, they do not express MYC. Postradiation atypical vascular lesions sometimes have an associated inflammatory infiltrate.⁹ Considerable histomorphologic overlap among lymphangiomas, atypical vascular lesions, and well-differentiated angiosarcomas exists; thus, lesions should be removed in their perceived totality whenever possible to help permit diagnostic distinction. In our patient, the abrupt discontinuation of vessels at the interface of the papillary and reticular dermis was reassuring of benignancy.

Our patient’s diagnosis of acquired cutaneous lymphangiectasia was a benign adverse effect of prior breast cancer treatments. This case demonstrates a rare dermatologic sequela that may arise in patients who receive surgical or radiation treatment of breast cancer. Given the heightened risk for angiosarcoma after radiation therapy as well as the increased risk for malignancy in patients with Cowden syndrome, biopsy can be an important diagnostic step in the management of these patients.

The Diagnosis: Acquired Cutaneous Lymphangiectasia

Histopathology showed a cluster of widely ectatic, thin-walled lymphatic spaces immediately subjacent to the epidermis and flanked by an epidermal collarette (Figure, A). The vessels did not extend any further than the papillary dermis and were not accompanied by any notable inflammation (Figure, B). A single layer of bland endothelial cells lined each lymphatic space (Figure, C). A diagnosis of acquired cutaneous lymphangiectasia secondary to surgical and radiation treatment of breast cancer was made. Clinical monitoring was recommended, but no treatment was required unless symptoms arose. At 2-year follow-up, she continued to do well.

Acquired cutaneous lymphangiectasia is characterized by benign dilations of surface lymphatic vessels, likely resulting from disruption of the lymphatic system.¹ This finding most commonly occurs on the external genitalia following combined surgical and radiation treatment of malignancy, though in a minority of cases it is seen with surgical or radiation treatment alone.² Acquired cutaneous lymphangiectasia secondary to radical mastectomy for breast cancer was first reported in 1956 in a patient with persistent ipsilateral lymphadenopathy.³ The presentation in a patient with Cowden syndrome is rare. Cowden syndrome (also called PTEN hamartoma tumor syndrome) is a rare autosomal-dominant disorder caused by mutations in the tumor suppressor phosphatase and tensin homolog gene, PTEN. It is characterized by multiple hamartomas and substantially increased risk for breast, endometrial, and thyroid malignancy.⁴ In addition to breast cancer, our patient had a history of papillary thyroid carcinoma, cerebellar dysplastic gangliocytoma, and multiple cutaneous fibromas and angiolipomas.

A diagnosis of syringomas—benign tumors that arise from the intraepidermal aspect of eccrine sweat ducts— could be considered in the differential diagnosis. Cases of eruptive syringoma on the breast have been reported, but the biopsy would show a circumscribed proliferation of tadpole-shaped tubules comprised of secretory cells in a sclerotic stroma.5 Hidrocystomas are benign sweat gland cysts that present on the face, especially around the eyes, but rarely have been reported on the trunk, particularly the axillae.6 Although they clinically manifest as translucent papules, histopathology shows fluid-filled cysts lined by a layer of secretory columnar epithelium.7 Metastatic breast carcinoma was considered, given the patient’s history of breast cancer. Cutaneous metastases often are found on the chest wall but also can occur at distant sites. Histopathology can reveal various patterns, including islands of tumor cells with glandular formation or single files of cells infiltrating through dermal collagen.

Angiosarcoma also must be considered in the setting of any vasoformative proliferation arising on previously irradiated skin. Angiosarcomas can sometimes be well differentiated with paradoxically bland cytomorphology but characteristically have anastomosing vessels and infiltrative architecture, which were not identified in our patient. Other diagnostic features of angiosarcoma include endothelial nuclear atypia, multilayering, and mitoses. Radiation-associated angiosarcomas amplify MYC, a transcription factor that affects multiple aspects of the cell cycle and is an oncogene implicated in several different types of malignancy.⁸MYC immunohistochemistry testing should be performed whenever a vasoformative proliferation on irradiated skin is partially sampled or shows any features concerning for angiosarcoma. Lastly, the term postradiation atypical vascular lesion has been introduced to describe discrete papular proliferations that show close histopathologic overlap with lymphangioma/lymphatic malformations. In contrast, atypical vascular lesions show wedge-shaped intradermal growth that can cause diagnostic confusion with well-differentiated angiosarcoma. Unlike angiosarcomas, they do not express MYC. Postradiation atypical vascular lesions sometimes have an associated inflammatory infiltrate.⁹ Considerable histomorphologic overlap among lymphangiomas, atypical vascular lesions, and well-differentiated angiosarcomas exists; thus, lesions should be removed in their perceived totality whenever possible to help permit diagnostic distinction. In our patient, the abrupt discontinuation of vessels at the interface of the papillary and reticular dermis was reassuring of benignancy.

Our patient’s diagnosis of acquired cutaneous lymphangiectasia was a benign adverse effect of prior breast cancer treatments. This case demonstrates a rare dermatologic sequela that may arise in patients who receive surgical or radiation treatment of breast cancer. Given the heightened risk for angiosarcoma after radiation therapy as well as the increased risk for malignancy in patients with Cowden syndrome, biopsy can be an important diagnostic step in the management of these patients.

The Diagnosis: Acquired Cutaneous Lymphangiectasia

Histopathology showed a cluster of widely ectatic, thin-walled lymphatic spaces immediately subjacent to the epidermis and flanked by an epidermal collarette (Figure, A). The vessels did not extend any further than the papillary dermis and were not accompanied by any notable inflammation (Figure, B). A single layer of bland endothelial cells lined each lymphatic space (Figure, C). A diagnosis of acquired cutaneous lymphangiectasia secondary to surgical and radiation treatment of breast cancer was made. Clinical monitoring was recommended, but no treatment was required unless symptoms arose. At 2-year follow-up, she continued to do well.

Acquired cutaneous lymphangiectasia is characterized by benign dilations of surface lymphatic vessels, likely resulting from disruption of the lymphatic system.¹ This finding most commonly occurs on the external genitalia following combined surgical and radiation treatment of malignancy, though in a minority of cases it is seen with surgical or radiation treatment alone.² Acquired cutaneous lymphangiectasia secondary to radical mastectomy for breast cancer was first reported in 1956 in a patient with persistent ipsilateral lymphadenopathy.³ The presentation in a patient with Cowden syndrome is rare. Cowden syndrome (also called PTEN hamartoma tumor syndrome) is a rare autosomal-dominant disorder caused by mutations in the tumor suppressor phosphatase and tensin homolog gene, PTEN. It is characterized by multiple hamartomas and substantially increased risk for breast, endometrial, and thyroid malignancy.⁴ In addition to breast cancer, our patient had a history of papillary thyroid carcinoma, cerebellar dysplastic gangliocytoma, and multiple cutaneous fibromas and angiolipomas.

A diagnosis of syringomas—benign tumors that arise from the intraepidermal aspect of eccrine sweat ducts— could be considered in the differential diagnosis. Cases of eruptive syringoma on the breast have been reported, but the biopsy would show a circumscribed proliferation of tadpole-shaped tubules comprised of secretory cells in a sclerotic stroma.5 Hidrocystomas are benign sweat gland cysts that present on the face, especially around the eyes, but rarely have been reported on the trunk, particularly the axillae.6 Although they clinically manifest as translucent papules, histopathology shows fluid-filled cysts lined by a layer of secretory columnar epithelium.7 Metastatic breast carcinoma was considered, given the patient’s history of breast cancer. Cutaneous metastases often are found on the chest wall but also can occur at distant sites. Histopathology can reveal various patterns, including islands of tumor cells with glandular formation or single files of cells infiltrating through dermal collagen.

Angiosarcoma also must be considered in the setting of any vasoformative proliferation arising on previously irradiated skin. Angiosarcomas can sometimes be well differentiated with paradoxically bland cytomorphology but characteristically have anastomosing vessels and infiltrative architecture, which were not identified in our patient. Other diagnostic features of angiosarcoma include endothelial nuclear atypia, multilayering, and mitoses. Radiation-associated angiosarcomas amplify MYC, a transcription factor that affects multiple aspects of the cell cycle and is an oncogene implicated in several different types of malignancy.⁸MYC immunohistochemistry testing should be performed whenever a vasoformative proliferation on irradiated skin is partially sampled or shows any features concerning for angiosarcoma. Lastly, the term postradiation atypical vascular lesion has been introduced to describe discrete papular proliferations that show close histopathologic overlap with lymphangioma/lymphatic malformations. In contrast, atypical vascular lesions show wedge-shaped intradermal growth that can cause diagnostic confusion with well-differentiated angiosarcoma. Unlike angiosarcomas, they do not express MYC. Postradiation atypical vascular lesions sometimes have an associated inflammatory infiltrate.⁹ Considerable histomorphologic overlap among lymphangiomas, atypical vascular lesions, and well-differentiated angiosarcomas exists; thus, lesions should be removed in their perceived totality whenever possible to help permit diagnostic distinction. In our patient, the abrupt discontinuation of vessels at the interface of the papillary and reticular dermis was reassuring of benignancy.

Our patient’s diagnosis of acquired cutaneous lymphangiectasia was a benign adverse effect of prior breast cancer treatments. This case demonstrates a rare dermatologic sequela that may arise in patients who receive surgical or radiation treatment of breast cancer. Given the heightened risk for angiosarcoma after radiation therapy as well as the increased risk for malignancy in patients with Cowden syndrome, biopsy can be an important diagnostic step in the management of these patients.

The Diagnosis: Proliferating Pilar Cyst

Histopathology revealed an extensive lobulated epithelial proliferation in a characteristic “rolls and scrolls” pattern (Figure 1). This finding along with the patient’s prior diagnosis of keratitis-ichthyosisdeafness (KID) syndrome supported the diagnosis of a proliferating pilar cyst.

Pilar (or trichilemmal) cysts are common dermal cysts typically found on the outer root sheath of hair follicles. They clinically manifest as multiple yellow dome-shaped nodules without central puncta. They are slow growing and histologically are characterized as cysts with a stratified squamous epithelium demonstrating lack of a granular layer (trichilemmal keratinization) with bright red keratin contents and central focal calcification (Figure 2). Pilar cysts are more common in adult women and may be inherited through an autosomal-dominant pattern.¹

Proliferating pilar cysts represent less than 3% of all pilar cysts.² In addition to the characteristic features of a pilar cyst, proliferating pilar cysts generally are larger (can be >6-cm wide) and are more ulcerative.³ Histopathology of proliferating pilar cysts reveals a more extensive epithelial proliferation, yielding a rolls and scrolls appearance, and may demonstrate nuclear atypia.⁴ Proliferating pilar cysts classically manifest as large, raised, smooth and/or ulcerated nodules on the scalp accompanied by areas of excessive hair growth in older women. They generally arise from pre-existing pilar cysts but also may occur sporadically.⁴

The development of multiple proliferating pilar cysts has been observed in patients with KID syndrome, a rare congenital ectodermal disorder characterized by a triad of vascularizing keratitis, hyperkeratosis, and sensorineural deafness.^5,6 It is caused by a missense mutation of the GJB2 gene encoding for connexin 26, a gap junction that facilitates intercellular signaling and is expressed in a variety of structures including the cochlea, cornea, sweat glands, and inner and outer root sheaths of hair follicles.⁷

The differential diagnosis for proliferating pilar cysts includes pilomatrixomas, squamous cell carcinomas, and malignant proliferating pilar tumors. Pilomatrixomas (or calcifying epitheliomas of Malherbe) are the most common adnexal skin tumors in the pediatric population and most commonly present on the head, neck, and arms.⁸ They also can manifest in adults. Pilomatrixomas are benign dermal-subcutaneous tumors encapsulated by connective tissue that are found on the hair matrix and are histologically characterized by basaloid cells, shadow (or ghost) cells, dystrophic calcifications, and giant cells.⁹ The amount of basaloid cells and shadow cells can vary. Tumor progression results in the enucleation of the basaloid cells to form eosinophilic shadow cells in which calcification can occur. Giant cell granulomas may form contiguous with the calcifications. Both proliferating pilar cysts and pilomatrixomas have a rolls and scrolls appearance on low-power microscopy, but the latter are differentiated by their shadow cells and basaloid areas (Figure 3).

Squamous cell carcinoma (SCC) is the second most common nonmelanoma skin cancer and more commonly affects men. Risk factors for SCC include immunosuppression and exposure to UV radiation. Histopathology of well-differentiated SCCs reveals invasive squamous cells with larger nuclei and a glassy appearance in addition to possible mitotic figures and keratin pearls (Figure 4). They typically manifest in sun-exposed areas such as the scalp, face, forearms, dorsal aspects of the hands, and lower legs.¹⁰ Proliferating pilar tumors often lack the nuclear atypia and invasive architecture of a well-differentiated SCC.

Features of malignant proliferating pilar tumors overlap with proliferating pilar cysts. In addition to the proliferative epithelium with abrupt trichilemmal keratinization that is typical of a proliferating pilar cyst, a malignant proliferating pilar tumor will demonstrate invasion into the surrounding tissue and lymph nodes, mitotic and architectural atypia, and necrosis (Figure 5).¹¹ Malignant proliferating pilar tumors grow rapidly, ranging in size from 1 to 10 cm, and may develop from pre-existing or proliferating pilar cysts or de novo.

The development of multiple proliferating pilar cysts and thus increased risk for progression to malignant proliferating pilar tumors has been observed in patients with KID syndrome.⁶ Our case highlights the importance of early screening and recognition of proliferating pilar tumors in patients with this condition.

The Diagnosis: Proliferating Pilar Cyst

Histopathology revealed an extensive lobulated epithelial proliferation in a characteristic “rolls and scrolls” pattern (Figure 1). This finding along with the patient’s prior diagnosis of keratitis-ichthyosisdeafness (KID) syndrome supported the diagnosis of a proliferating pilar cyst.

Pilar (or trichilemmal) cysts are common dermal cysts typically found on the outer root sheath of hair follicles. They clinically manifest as multiple yellow dome-shaped nodules without central puncta. They are slow growing and histologically are characterized as cysts with a stratified squamous epithelium demonstrating lack of a granular layer (trichilemmal keratinization) with bright red keratin contents and central focal calcification (Figure 2). Pilar cysts are more common in adult women and may be inherited through an autosomal-dominant pattern.¹

Proliferating pilar cysts represent less than 3% of all pilar cysts.² In addition to the characteristic features of a pilar cyst, proliferating pilar cysts generally are larger (can be >6-cm wide) and are more ulcerative.³ Histopathology of proliferating pilar cysts reveals a more extensive epithelial proliferation, yielding a rolls and scrolls appearance, and may demonstrate nuclear atypia.⁴ Proliferating pilar cysts classically manifest as large, raised, smooth and/or ulcerated nodules on the scalp accompanied by areas of excessive hair growth in older women. They generally arise from pre-existing pilar cysts but also may occur sporadically.⁴

The development of multiple proliferating pilar cysts has been observed in patients with KID syndrome, a rare congenital ectodermal disorder characterized by a triad of vascularizing keratitis, hyperkeratosis, and sensorineural deafness.^5,6 It is caused by a missense mutation of the GJB2 gene encoding for connexin 26, a gap junction that facilitates intercellular signaling and is expressed in a variety of structures including the cochlea, cornea, sweat glands, and inner and outer root sheaths of hair follicles.⁷

The differential diagnosis for proliferating pilar cysts includes pilomatrixomas, squamous cell carcinomas, and malignant proliferating pilar tumors. Pilomatrixomas (or calcifying epitheliomas of Malherbe) are the most common adnexal skin tumors in the pediatric population and most commonly present on the head, neck, and arms.⁸ They also can manifest in adults. Pilomatrixomas are benign dermal-subcutaneous tumors encapsulated by connective tissue that are found on the hair matrix and are histologically characterized by basaloid cells, shadow (or ghost) cells, dystrophic calcifications, and giant cells.⁹ The amount of basaloid cells and shadow cells can vary. Tumor progression results in the enucleation of the basaloid cells to form eosinophilic shadow cells in which calcification can occur. Giant cell granulomas may form contiguous with the calcifications. Both proliferating pilar cysts and pilomatrixomas have a rolls and scrolls appearance on low-power microscopy, but the latter are differentiated by their shadow cells and basaloid areas (Figure 3).

Squamous cell carcinoma (SCC) is the second most common nonmelanoma skin cancer and more commonly affects men. Risk factors for SCC include immunosuppression and exposure to UV radiation. Histopathology of well-differentiated SCCs reveals invasive squamous cells with larger nuclei and a glassy appearance in addition to possible mitotic figures and keratin pearls (Figure 4). They typically manifest in sun-exposed areas such as the scalp, face, forearms, dorsal aspects of the hands, and lower legs.¹⁰ Proliferating pilar tumors often lack the nuclear atypia and invasive architecture of a well-differentiated SCC.

Features of malignant proliferating pilar tumors overlap with proliferating pilar cysts. In addition to the proliferative epithelium with abrupt trichilemmal keratinization that is typical of a proliferating pilar cyst, a malignant proliferating pilar tumor will demonstrate invasion into the surrounding tissue and lymph nodes, mitotic and architectural atypia, and necrosis (Figure 5).¹¹ Malignant proliferating pilar tumors grow rapidly, ranging in size from 1 to 10 cm, and may develop from pre-existing or proliferating pilar cysts or de novo.

The development of multiple proliferating pilar cysts and thus increased risk for progression to malignant proliferating pilar tumors has been observed in patients with KID syndrome.⁶ Our case highlights the importance of early screening and recognition of proliferating pilar tumors in patients with this condition.

The Diagnosis: Proliferating Pilar Cyst

Histopathology revealed an extensive lobulated epithelial proliferation in a characteristic “rolls and scrolls” pattern (Figure 1). This finding along with the patient’s prior diagnosis of keratitis-ichthyosisdeafness (KID) syndrome supported the diagnosis of a proliferating pilar cyst.

Pilar (or trichilemmal) cysts are common dermal cysts typically found on the outer root sheath of hair follicles. They clinically manifest as multiple yellow dome-shaped nodules without central puncta. They are slow growing and histologically are characterized as cysts with a stratified squamous epithelium demonstrating lack of a granular layer (trichilemmal keratinization) with bright red keratin contents and central focal calcification (Figure 2). Pilar cysts are more common in adult women and may be inherited through an autosomal-dominant pattern.¹

Proliferating pilar cysts represent less than 3% of all pilar cysts.² In addition to the characteristic features of a pilar cyst, proliferating pilar cysts generally are larger (can be >6-cm wide) and are more ulcerative.³ Histopathology of proliferating pilar cysts reveals a more extensive epithelial proliferation, yielding a rolls and scrolls appearance, and may demonstrate nuclear atypia.⁴ Proliferating pilar cysts classically manifest as large, raised, smooth and/or ulcerated nodules on the scalp accompanied by areas of excessive hair growth in older women. They generally arise from pre-existing pilar cysts but also may occur sporadically.⁴

The development of multiple proliferating pilar cysts has been observed in patients with KID syndrome, a rare congenital ectodermal disorder characterized by a triad of vascularizing keratitis, hyperkeratosis, and sensorineural deafness.^5,6 It is caused by a missense mutation of the GJB2 gene encoding for connexin 26, a gap junction that facilitates intercellular signaling and is expressed in a variety of structures including the cochlea, cornea, sweat glands, and inner and outer root sheaths of hair follicles.⁷

The differential diagnosis for proliferating pilar cysts includes pilomatrixomas, squamous cell carcinomas, and malignant proliferating pilar tumors. Pilomatrixomas (or calcifying epitheliomas of Malherbe) are the most common adnexal skin tumors in the pediatric population and most commonly present on the head, neck, and arms.⁸ They also can manifest in adults. Pilomatrixomas are benign dermal-subcutaneous tumors encapsulated by connective tissue that are found on the hair matrix and are histologically characterized by basaloid cells, shadow (or ghost) cells, dystrophic calcifications, and giant cells.⁹ The amount of basaloid cells and shadow cells can vary. Tumor progression results in the enucleation of the basaloid cells to form eosinophilic shadow cells in which calcification can occur. Giant cell granulomas may form contiguous with the calcifications. Both proliferating pilar cysts and pilomatrixomas have a rolls and scrolls appearance on low-power microscopy, but the latter are differentiated by their shadow cells and basaloid areas (Figure 3).

Squamous cell carcinoma (SCC) is the second most common nonmelanoma skin cancer and more commonly affects men. Risk factors for SCC include immunosuppression and exposure to UV radiation. Histopathology of well-differentiated SCCs reveals invasive squamous cells with larger nuclei and a glassy appearance in addition to possible mitotic figures and keratin pearls (Figure 4). They typically manifest in sun-exposed areas such as the scalp, face, forearms, dorsal aspects of the hands, and lower legs.¹⁰ Proliferating pilar tumors often lack the nuclear atypia and invasive architecture of a well-differentiated SCC.

Features of malignant proliferating pilar tumors overlap with proliferating pilar cysts. In addition to the proliferative epithelium with abrupt trichilemmal keratinization that is typical of a proliferating pilar cyst, a malignant proliferating pilar tumor will demonstrate invasion into the surrounding tissue and lymph nodes, mitotic and architectural atypia, and necrosis (Figure 5).¹¹ Malignant proliferating pilar tumors grow rapidly, ranging in size from 1 to 10 cm, and may develop from pre-existing or proliferating pilar cysts or de novo.

The development of multiple proliferating pilar cysts and thus increased risk for progression to malignant proliferating pilar tumors has been observed in patients with KID syndrome.⁶ Our case highlights the importance of early screening and recognition of proliferating pilar tumors in patients with this condition.

To the Editor:

Necrotizing myositis (NM) is an exceedingly rare necrotizing soft-tissue infection (NSTI) that is characterized by skeletal muscle involvement. β -Hemolytic streptococci, such as Streptococcus pyogenes , are the most common causative organisms. The overall prevalence and incidence of NM is unknown. A review of the literature by Adams et al ² identified only 21 cases between 1900 and 1985.

Timely treatment of this infection leads to improved outcomes, but diagnosis can be challenging due to the ambiguous presentation of NM and lack of specific cutaneous changes.³ Clinical manifestations including bullae, blisters, vesicles, and petechiae become more prominent as infection progresses.⁴ If NM is suspected due to cutaneous manifestations, it is imperative that the underlying cause be identified; for example, NM must be distinguished from the overlapping presentation of pyoderma gangrenosum (PG). Because NM has nearly 100% mortality without prompt surgical intervention, early identification is critical.⁵ Herein, we report a case of NM that illustrates the correlation of clinical, histological, and imaging findings required to diagnose this potentially fatal infection.

An 80-year-old man presented to the emergency department with worsening pain, edema, and spreading redness of the right wrist over the last 5 weeks. He had a history of atopic dermatitis that was refractory to topical steroids and methotrexate; he was dependent on an oral steroid (prednisone 30 mg/d) for symptom control. The patient reported minor trauma to the area after performing home renovations. He received numerous rounds of oral antibiotics as an outpatient for presumed cellulitis and reported he was “getting better” but that the signs and symptoms of the condition grew worse after outpatient arthrocentesis. Dermatology was consulted to evaluate for a necrotizing neutrophilic dermatosis such as PG.

At the current presentation, the patient was tachycardic and afebrile (temperature, 98.2 °F [36.8 °C]). Physical examination revealed large, exquisitely tender, ill-defined necrotic ulceration of the right wrist with purulent debris and diffuse edema (Figure 1). Sequential evaluation at 6-hour intervals revealed notably increasing purulence, edema, and tenderness. Interconnected sinus tracts that extended to the fascial plane were observed.

Laboratory workup was notable for a markedly elevated C-reactive protein level of 18.9 mg/dL (reference range, 0–0.8 mg/dL) and an elevated white blood cell count of 19.92×10⁹/L (reference range, 4.5–11.0×10⁹/L). Blood and tissue cultures were positive for methicillin-sensitive Staphylococcus aureus. Computed tomography and magnetic resonance imaging (MRI) prior to biopsy demonstrated findings consistent with extensive subcutaneous and intramuscular areas of loculation and foci of gas (Figure 2). These findings were consistent with intramuscular involvement. A punch biopsy revealed a necrotic epidermis filled with neutrophilic pustules and a dense dermal infiltrate of neutrophilic inflammation consistent with infection (Figure 3).

Emergency surgery was performed with debridement of necrotic tissue and muscle. Postoperatively, he became more clinically stable after being placed on cefazolin through a peripherally inserted central catheter. He underwent 4 additional washouts over the ensuing month, as well as tendon reconstructions, a radial forearm flap, and reverse radial forearm flap reconstruction of the forearm. At the time of publication, there has been no recurrence. The patient’s atopic dermatitis is well controlled on dupilumab and topical fluocinonide alone, with a recent IgA level of 1 g/L and a body surface area measurement of 2%. Dupilumab was started 3 months after surgery.

Necrotizing myositis is a rare, rapidly progressive infection involving muscle that can manifest as superficial cutaneous involvement. The clinical manifestation of NM is harder to recognize than other NSTIs such as necrotizing fasciitis, likely due to the initial prodromal phase of NM, which consists of nonspecific constitutional symptoms.³ Systemic findings such as tachycardia, fever, hypotension, and shock occur in only 10% to 40% of NM patients.^4,5

In our patient, clues of NM included fulfillment of criteria for systemic inflammatory response syndrome at admission and a presumed source of infection; taken together, these findings should lead to a diagnosis of sepsis until otherwise proven. The patient also reported pain that was not proportional to the skin findings, which suggested an NSTI. His lack of constitutional symptoms may have been due to the effects of prednisone, which was changed to dupilumab during hospitalization.

The clinical and histological findings of NM are nonspecific. Clinical findings include skin discoloration with bullae, blisters, vesicles, or petechiae.⁴ Our case adds to the descriptive morphology by including marked edema with ulceration, progressive purulence, and interconnected sinuses tracking to the fascial plane. Histologic findings can include confluent necrosis extending from the epidermis to the underlying muscle with dense neutrophilic inflammation. Notably, these findings can mirror necrotizing neutrophilic dermatoses in the absence of an infectious cause. Failure to recognize simple systemic inflammatory response syndrome criteria in NM patients due to slow treatment response or incorrect treatment can can lead to loss of a limb or death.

Workup reveals overlap with necrotizing neutrophilic dermatoses including PG, which is the prototypical neutrophilic dermatosis. Morphologically, PG presents as an ulcer with a purple and undermined border, often having developed from an initial papule, vesicle, or pustule. A neutrophilic infiltrate of the ulcer edge is the major criterion required to diagnose PG⁶; minor criteria include a positive pathergy test, history of inflammatory arthritis or inflammatory bowel disease, and exclusion of infection.⁶ When compared directly to an NSTI such as NM, the most important variable that sets PG apart is the absence of bacterial growth on blood and tissue cultures.⁷

Imaging studies can aid in the clinical diagnosis of NM and help distinguish the disease from PG. Computed tomography and MRI may demonstrate hallmarks of extensive necrotizing infection, such as gas formation and consequent fascial swelling, thickening and edema of involved muscle, and subfascial fluid collection.^3,4 Distinct from NM, imaging findings in PG are more subtle, suggesting cellulitic inflammation with edema.⁸ A defining radiographic feature of NM can be foci of gas within muscle or fascia, though absence of this finding does not exclude NM.^1,4

In conclusion, NM is a rare intramuscular infection that can be difficult to diagnose due to its nonspecific presentation and lack of constitutional symptoms. Dermatologists should maintain a high level of suspicion for NM in the setting of rapidly progressive clinical findings; accurate diagnosis requires a multimodal approach with complete correlation of clinical, histological, and imaging findings. Computed tomography and MRI can heighten the approach, even when necrotizing neutrophilic dermatoses and NM have similar clinical and histological appearances. Once a diagnosis of NM is established, prompt surgical and medical intervention improves the prognosis.

To the Editor:

Necrotizing myositis (NM) is an exceedingly rare necrotizing soft-tissue infection (NSTI) that is characterized by skeletal muscle involvement. β -Hemolytic streptococci, such as Streptococcus pyogenes , are the most common causative organisms. The overall prevalence and incidence of NM is unknown. A review of the literature by Adams et al ² identified only 21 cases between 1900 and 1985.

Timely treatment of this infection leads to improved outcomes, but diagnosis can be challenging due to the ambiguous presentation of NM and lack of specific cutaneous changes.³ Clinical manifestations including bullae, blisters, vesicles, and petechiae become more prominent as infection progresses.⁴ If NM is suspected due to cutaneous manifestations, it is imperative that the underlying cause be identified; for example, NM must be distinguished from the overlapping presentation of pyoderma gangrenosum (PG). Because NM has nearly 100% mortality without prompt surgical intervention, early identification is critical.⁵ Herein, we report a case of NM that illustrates the correlation of clinical, histological, and imaging findings required to diagnose this potentially fatal infection.

An 80-year-old man presented to the emergency department with worsening pain, edema, and spreading redness of the right wrist over the last 5 weeks. He had a history of atopic dermatitis that was refractory to topical steroids and methotrexate; he was dependent on an oral steroid (prednisone 30 mg/d) for symptom control. The patient reported minor trauma to the area after performing home renovations. He received numerous rounds of oral antibiotics as an outpatient for presumed cellulitis and reported he was “getting better” but that the signs and symptoms of the condition grew worse after outpatient arthrocentesis. Dermatology was consulted to evaluate for a necrotizing neutrophilic dermatosis such as PG.

At the current presentation, the patient was tachycardic and afebrile (temperature, 98.2 °F [36.8 °C]). Physical examination revealed large, exquisitely tender, ill-defined necrotic ulceration of the right wrist with purulent debris and diffuse edema (Figure 1). Sequential evaluation at 6-hour intervals revealed notably increasing purulence, edema, and tenderness. Interconnected sinus tracts that extended to the fascial plane were observed.

Laboratory workup was notable for a markedly elevated C-reactive protein level of 18.9 mg/dL (reference range, 0–0.8 mg/dL) and an elevated white blood cell count of 19.92×10⁹/L (reference range, 4.5–11.0×10⁹/L). Blood and tissue cultures were positive for methicillin-sensitive Staphylococcus aureus. Computed tomography and magnetic resonance imaging (MRI) prior to biopsy demonstrated findings consistent with extensive subcutaneous and intramuscular areas of loculation and foci of gas (Figure 2). These findings were consistent with intramuscular involvement. A punch biopsy revealed a necrotic epidermis filled with neutrophilic pustules and a dense dermal infiltrate of neutrophilic inflammation consistent with infection (Figure 3).

Emergency surgery was performed with debridement of necrotic tissue and muscle. Postoperatively, he became more clinically stable after being placed on cefazolin through a peripherally inserted central catheter. He underwent 4 additional washouts over the ensuing month, as well as tendon reconstructions, a radial forearm flap, and reverse radial forearm flap reconstruction of the forearm. At the time of publication, there has been no recurrence. The patient’s atopic dermatitis is well controlled on dupilumab and topical fluocinonide alone, with a recent IgA level of 1 g/L and a body surface area measurement of 2%. Dupilumab was started 3 months after surgery.

Necrotizing myositis is a rare, rapidly progressive infection involving muscle that can manifest as superficial cutaneous involvement. The clinical manifestation of NM is harder to recognize than other NSTIs such as necrotizing fasciitis, likely due to the initial prodromal phase of NM, which consists of nonspecific constitutional symptoms.³ Systemic findings such as tachycardia, fever, hypotension, and shock occur in only 10% to 40% of NM patients.^4,5

In our patient, clues of NM included fulfillment of criteria for systemic inflammatory response syndrome at admission and a presumed source of infection; taken together, these findings should lead to a diagnosis of sepsis until otherwise proven. The patient also reported pain that was not proportional to the skin findings, which suggested an NSTI. His lack of constitutional symptoms may have been due to the effects of prednisone, which was changed to dupilumab during hospitalization.

The clinical and histological findings of NM are nonspecific. Clinical findings include skin discoloration with bullae, blisters, vesicles, or petechiae.⁴ Our case adds to the descriptive morphology by including marked edema with ulceration, progressive purulence, and interconnected sinuses tracking to the fascial plane. Histologic findings can include confluent necrosis extending from the epidermis to the underlying muscle with dense neutrophilic inflammation. Notably, these findings can mirror necrotizing neutrophilic dermatoses in the absence of an infectious cause. Failure to recognize simple systemic inflammatory response syndrome criteria in NM patients due to slow treatment response or incorrect treatment can can lead to loss of a limb or death.

Workup reveals overlap with necrotizing neutrophilic dermatoses including PG, which is the prototypical neutrophilic dermatosis. Morphologically, PG presents as an ulcer with a purple and undermined border, often having developed from an initial papule, vesicle, or pustule. A neutrophilic infiltrate of the ulcer edge is the major criterion required to diagnose PG⁶; minor criteria include a positive pathergy test, history of inflammatory arthritis or inflammatory bowel disease, and exclusion of infection.⁶ When compared directly to an NSTI such as NM, the most important variable that sets PG apart is the absence of bacterial growth on blood and tissue cultures.⁷

Imaging studies can aid in the clinical diagnosis of NM and help distinguish the disease from PG. Computed tomography and MRI may demonstrate hallmarks of extensive necrotizing infection, such as gas formation and consequent fascial swelling, thickening and edema of involved muscle, and subfascial fluid collection.^3,4 Distinct from NM, imaging findings in PG are more subtle, suggesting cellulitic inflammation with edema.⁸ A defining radiographic feature of NM can be foci of gas within muscle or fascia, though absence of this finding does not exclude NM.^1,4

In conclusion, NM is a rare intramuscular infection that can be difficult to diagnose due to its nonspecific presentation and lack of constitutional symptoms. Dermatologists should maintain a high level of suspicion for NM in the setting of rapidly progressive clinical findings; accurate diagnosis requires a multimodal approach with complete correlation of clinical, histological, and imaging findings. Computed tomography and MRI can heighten the approach, even when necrotizing neutrophilic dermatoses and NM have similar clinical and histological appearances. Once a diagnosis of NM is established, prompt surgical and medical intervention improves the prognosis.

To the Editor:

Necrotizing myositis (NM) is an exceedingly rare necrotizing soft-tissue infection (NSTI) that is characterized by skeletal muscle involvement. β -Hemolytic streptococci, such as Streptococcus pyogenes , are the most common causative organisms. The overall prevalence and incidence of NM is unknown. A review of the literature by Adams et al ² identified only 21 cases between 1900 and 1985.

Timely treatment of this infection leads to improved outcomes, but diagnosis can be challenging due to the ambiguous presentation of NM and lack of specific cutaneous changes.³ Clinical manifestations including bullae, blisters, vesicles, and petechiae become more prominent as infection progresses.⁴ If NM is suspected due to cutaneous manifestations, it is imperative that the underlying cause be identified; for example, NM must be distinguished from the overlapping presentation of pyoderma gangrenosum (PG). Because NM has nearly 100% mortality without prompt surgical intervention, early identification is critical.⁵ Herein, we report a case of NM that illustrates the correlation of clinical, histological, and imaging findings required to diagnose this potentially fatal infection.

An 80-year-old man presented to the emergency department with worsening pain, edema, and spreading redness of the right wrist over the last 5 weeks. He had a history of atopic dermatitis that was refractory to topical steroids and methotrexate; he was dependent on an oral steroid (prednisone 30 mg/d) for symptom control. The patient reported minor trauma to the area after performing home renovations. He received numerous rounds of oral antibiotics as an outpatient for presumed cellulitis and reported he was “getting better” but that the signs and symptoms of the condition grew worse after outpatient arthrocentesis. Dermatology was consulted to evaluate for a necrotizing neutrophilic dermatosis such as PG.

At the current presentation, the patient was tachycardic and afebrile (temperature, 98.2 °F [36.8 °C]). Physical examination revealed large, exquisitely tender, ill-defined necrotic ulceration of the right wrist with purulent debris and diffuse edema (Figure 1). Sequential evaluation at 6-hour intervals revealed notably increasing purulence, edema, and tenderness. Interconnected sinus tracts that extended to the fascial plane were observed.

Laboratory workup was notable for a markedly elevated C-reactive protein level of 18.9 mg/dL (reference range, 0–0.8 mg/dL) and an elevated white blood cell count of 19.92×10⁹/L (reference range, 4.5–11.0×10⁹/L). Blood and tissue cultures were positive for methicillin-sensitive Staphylococcus aureus. Computed tomography and magnetic resonance imaging (MRI) prior to biopsy demonstrated findings consistent with extensive subcutaneous and intramuscular areas of loculation and foci of gas (Figure 2). These findings were consistent with intramuscular involvement. A punch biopsy revealed a necrotic epidermis filled with neutrophilic pustules and a dense dermal infiltrate of neutrophilic inflammation consistent with infection (Figure 3).

Emergency surgery was performed with debridement of necrotic tissue and muscle. Postoperatively, he became more clinically stable after being placed on cefazolin through a peripherally inserted central catheter. He underwent 4 additional washouts over the ensuing month, as well as tendon reconstructions, a radial forearm flap, and reverse radial forearm flap reconstruction of the forearm. At the time of publication, there has been no recurrence. The patient’s atopic dermatitis is well controlled on dupilumab and topical fluocinonide alone, with a recent IgA level of 1 g/L and a body surface area measurement of 2%. Dupilumab was started 3 months after surgery.

Necrotizing myositis is a rare, rapidly progressive infection involving muscle that can manifest as superficial cutaneous involvement. The clinical manifestation of NM is harder to recognize than other NSTIs such as necrotizing fasciitis, likely due to the initial prodromal phase of NM, which consists of nonspecific constitutional symptoms.³ Systemic findings such as tachycardia, fever, hypotension, and shock occur in only 10% to 40% of NM patients.^4,5

In our patient, clues of NM included fulfillment of criteria for systemic inflammatory response syndrome at admission and a presumed source of infection; taken together, these findings should lead to a diagnosis of sepsis until otherwise proven. The patient also reported pain that was not proportional to the skin findings, which suggested an NSTI. His lack of constitutional symptoms may have been due to the effects of prednisone, which was changed to dupilumab during hospitalization.

The clinical and histological findings of NM are nonspecific. Clinical findings include skin discoloration with bullae, blisters, vesicles, or petechiae.⁴ Our case adds to the descriptive morphology by including marked edema with ulceration, progressive purulence, and interconnected sinuses tracking to the fascial plane. Histologic findings can include confluent necrosis extending from the epidermis to the underlying muscle with dense neutrophilic inflammation. Notably, these findings can mirror necrotizing neutrophilic dermatoses in the absence of an infectious cause. Failure to recognize simple systemic inflammatory response syndrome criteria in NM patients due to slow treatment response or incorrect treatment can can lead to loss of a limb or death.

Workup reveals overlap with necrotizing neutrophilic dermatoses including PG, which is the prototypical neutrophilic dermatosis. Morphologically, PG presents as an ulcer with a purple and undermined border, often having developed from an initial papule, vesicle, or pustule. A neutrophilic infiltrate of the ulcer edge is the major criterion required to diagnose PG⁶; minor criteria include a positive pathergy test, history of inflammatory arthritis or inflammatory bowel disease, and exclusion of infection.⁶ When compared directly to an NSTI such as NM, the most important variable that sets PG apart is the absence of bacterial growth on blood and tissue cultures.⁷

Imaging studies can aid in the clinical diagnosis of NM and help distinguish the disease from PG. Computed tomography and MRI may demonstrate hallmarks of extensive necrotizing infection, such as gas formation and consequent fascial swelling, thickening and edema of involved muscle, and subfascial fluid collection.^3,4 Distinct from NM, imaging findings in PG are more subtle, suggesting cellulitic inflammation with edema.⁸ A defining radiographic feature of NM can be foci of gas within muscle or fascia, though absence of this finding does not exclude NM.^1,4

In conclusion, NM is a rare intramuscular infection that can be difficult to diagnose due to its nonspecific presentation and lack of constitutional symptoms. Dermatologists should maintain a high level of suspicion for NM in the setting of rapidly progressive clinical findings; accurate diagnosis requires a multimodal approach with complete correlation of clinical, histological, and imaging findings. Computed tomography and MRI can heighten the approach, even when necrotizing neutrophilic dermatoses and NM have similar clinical and histological appearances. Once a diagnosis of NM is established, prompt surgical and medical intervention improves the prognosis.

To the Editor:

Kaposi sarcoma (KS) is a rare angioproliferative disorder associated with human herpesvirus 8 (HHV-8) infection.¹ There are 4 main recognized epidemiologic forms of KS: classic, endemic, epidemic, and iatrogenic (Table). Nonepidemic KS is a recently described rare fifth type of KS that occurs in a subset of patients who do not fit the other classifications—HIV-negative patients without detectable cellular or humoral immune deficiency. This subset has been described as clinically similar to classic KS with limited disease but occurring in younger men.^2,3 We describe a case of nonepidemic KS in a Middle Eastern heterosexual immunocompetent man.

A 30-year-old man presented for evaluation of a growth on the nose of 3 months’ duration. The patient reported being otherwise healthy and was not taking long-term medications. He denied a history of malignancy, organ transplant, or immunosuppressive therapy. He was born in Syria and lived in Thailand for several years prior to moving to the United States. HIV testing 6 months prior to presentation was negative. He denied fever, chills, lymphadenopathy, shortness of breath, hemoptysis, melena, hematochezia, and intravenous drug use.

Physical examination revealed a solitary shiny, 7-mm, pink-red papule on the nasal dorsum (Figure 1). No other skin or mucosal lesions were identified. There was no cervical, axillary, or inguinal lymphadenopathy. A laboratory workup consisting of serum immunoglobulins and serum protein electrophoresis was unremarkable. Tests for HIV-1 and HIV-2 as well as human T-lymphotropic virus 1 and 2 were negative. The CD4 and CD8 counts were within reference range. Histopathology of a shave biopsy revealed a dermal spindle cell proliferation arranged in short intersecting fascicles and admixed with plasma cells and occasional mitotic figures. Immunohistochemistry showed that the spindle cells stained positive for CD34, CD31, and HHV-8 (Figure 2). The lesion resolved after treatment with cryotherapy. Repeat HIV testing 3 months later was negative. No recurrence or new lesions were identified at 3-month follow-up.

Similar to the other subtypes of KS, the nonepidemic form is dependent on HHV-8 infection, which is more commonly transmitted via saliva and sexual contact.^3,4 After infecting endothelial cells, HHV-8 is believed to activate the mammalian target of rapamycin and nuclear factor κB pathways, resulting in aberrant cellular differentiation and neoangiogenesis through upregulation of vascular endothelial growth factor and basic fibroblast growth factor.^2,4 Similar to what is seen with other herpesviruses, HHV-8 infection typically is lifelong due to the virus’s ability to establish latency within human B cells and endothelial cells as well as undergo sporadic bouts of lytic reactivation during its life cycle.⁴

Nonepidemic KS resembles other variants clinically, manifesting as erythematous or violaceous, painless, nonblanchable macules, papules, and nodules.¹ Early lesions often are asymptomatic and can manifest as pigmented macules or small papules that vary from pale pink to vivid purple. Nodules also can occur and be exophytic and ulcerated with bleeding.¹ Secondary lymphoproliferative disorders including Castleman disease and lymphoma have been reported.^2,5

In contrast to other types of KS in which pulmonary or gastrointestinal tract lesions can develop with hemoptysis or hematochezia, mucocutaneous and visceral lesions rarely are reported in nonepidemic KS.³ Lymphedema, a feature associated with endemic KS, is notably absent in nonepidemic KS.^1,3

The differential diagnosis applicable to all KS subtypes includes other vascular lesions such as angiomatosis and angiosarcoma. Histopathologic analysis is critical to differentiate KS from these conditions; visual diagnosis alone has only an 80% positive predictive value for KS.⁴ The histopathologic presentation of KS is a vascular proliferation in the dermis accompanied by an increased number of vessels without an endothelial cell lining.⁴ Spindle cell proliferation also is a common feature and is considered to be the KS tumor cell. Immunostaining for HHV-8 antigen as well as for CD31 and CD34 can be used to confirm the diagnosis.⁴

The management and prognosis of KS depends on the epidemiologic subtype. Classic and nonepidemic KS generally are indolent with a good prognosis. Periodic follow-up is recommended because of an increased risk for secondary malignancy such as lymphoma. The treatment of epidemic KS is highly active antiretroviral therapy. Similarly, reduction of immunosuppression is warranted for iatrogenic KS. For all types, cutaneous lesions can be treated with local excision, cryosurgery, radiation, chemotherapy, intralesional vincristine, or a topical agent such as imiquimod or alitretinoin.⁶

To the Editor:

Kaposi sarcoma (KS) is a rare angioproliferative disorder associated with human herpesvirus 8 (HHV-8) infection.¹ There are 4 main recognized epidemiologic forms of KS: classic, endemic, epidemic, and iatrogenic (Table). Nonepidemic KS is a recently described rare fifth type of KS that occurs in a subset of patients who do not fit the other classifications—HIV-negative patients without detectable cellular or humoral immune deficiency. This subset has been described as clinically similar to classic KS with limited disease but occurring in younger men.^2,3 We describe a case of nonepidemic KS in a Middle Eastern heterosexual immunocompetent man.

A 30-year-old man presented for evaluation of a growth on the nose of 3 months’ duration. The patient reported being otherwise healthy and was not taking long-term medications. He denied a history of malignancy, organ transplant, or immunosuppressive therapy. He was born in Syria and lived in Thailand for several years prior to moving to the United States. HIV testing 6 months prior to presentation was negative. He denied fever, chills, lymphadenopathy, shortness of breath, hemoptysis, melena, hematochezia, and intravenous drug use.

Physical examination revealed a solitary shiny, 7-mm, pink-red papule on the nasal dorsum (Figure 1). No other skin or mucosal lesions were identified. There was no cervical, axillary, or inguinal lymphadenopathy. A laboratory workup consisting of serum immunoglobulins and serum protein electrophoresis was unremarkable. Tests for HIV-1 and HIV-2 as well as human T-lymphotropic virus 1 and 2 were negative. The CD4 and CD8 counts were within reference range. Histopathology of a shave biopsy revealed a dermal spindle cell proliferation arranged in short intersecting fascicles and admixed with plasma cells and occasional mitotic figures. Immunohistochemistry showed that the spindle cells stained positive for CD34, CD31, and HHV-8 (Figure 2). The lesion resolved after treatment with cryotherapy. Repeat HIV testing 3 months later was negative. No recurrence or new lesions were identified at 3-month follow-up.

Similar to the other subtypes of KS, the nonepidemic form is dependent on HHV-8 infection, which is more commonly transmitted via saliva and sexual contact.^3,4 After infecting endothelial cells, HHV-8 is believed to activate the mammalian target of rapamycin and nuclear factor κB pathways, resulting in aberrant cellular differentiation and neoangiogenesis through upregulation of vascular endothelial growth factor and basic fibroblast growth factor.^2,4 Similar to what is seen with other herpesviruses, HHV-8 infection typically is lifelong due to the virus’s ability to establish latency within human B cells and endothelial cells as well as undergo sporadic bouts of lytic reactivation during its life cycle.⁴

Nonepidemic KS resembles other variants clinically, manifesting as erythematous or violaceous, painless, nonblanchable macules, papules, and nodules.¹ Early lesions often are asymptomatic and can manifest as pigmented macules or small papules that vary from pale pink to vivid purple. Nodules also can occur and be exophytic and ulcerated with bleeding.¹ Secondary lymphoproliferative disorders including Castleman disease and lymphoma have been reported.^2,5

In contrast to other types of KS in which pulmonary or gastrointestinal tract lesions can develop with hemoptysis or hematochezia, mucocutaneous and visceral lesions rarely are reported in nonepidemic KS.³ Lymphedema, a feature associated with endemic KS, is notably absent in nonepidemic KS.^1,3

The differential diagnosis applicable to all KS subtypes includes other vascular lesions such as angiomatosis and angiosarcoma. Histopathologic analysis is critical to differentiate KS from these conditions; visual diagnosis alone has only an 80% positive predictive value for KS.⁴ The histopathologic presentation of KS is a vascular proliferation in the dermis accompanied by an increased number of vessels without an endothelial cell lining.⁴ Spindle cell proliferation also is a common feature and is considered to be the KS tumor cell. Immunostaining for HHV-8 antigen as well as for CD31 and CD34 can be used to confirm the diagnosis.⁴

The management and prognosis of KS depends on the epidemiologic subtype. Classic and nonepidemic KS generally are indolent with a good prognosis. Periodic follow-up is recommended because of an increased risk for secondary malignancy such as lymphoma. The treatment of epidemic KS is highly active antiretroviral therapy. Similarly, reduction of immunosuppression is warranted for iatrogenic KS. For all types, cutaneous lesions can be treated with local excision, cryosurgery, radiation, chemotherapy, intralesional vincristine, or a topical agent such as imiquimod or alitretinoin.⁶

To the Editor:

Kaposi sarcoma (KS) is a rare angioproliferative disorder associated with human herpesvirus 8 (HHV-8) infection.¹ There are 4 main recognized epidemiologic forms of KS: classic, endemic, epidemic, and iatrogenic (Table). Nonepidemic KS is a recently described rare fifth type of KS that occurs in a subset of patients who do not fit the other classifications—HIV-negative patients without detectable cellular or humoral immune deficiency. This subset has been described as clinically similar to classic KS with limited disease but occurring in younger men.^2,3 We describe a case of nonepidemic KS in a Middle Eastern heterosexual immunocompetent man.

A 30-year-old man presented for evaluation of a growth on the nose of 3 months’ duration. The patient reported being otherwise healthy and was not taking long-term medications. He denied a history of malignancy, organ transplant, or immunosuppressive therapy. He was born in Syria and lived in Thailand for several years prior to moving to the United States. HIV testing 6 months prior to presentation was negative. He denied fever, chills, lymphadenopathy, shortness of breath, hemoptysis, melena, hematochezia, and intravenous drug use.

Physical examination revealed a solitary shiny, 7-mm, pink-red papule on the nasal dorsum (Figure 1). No other skin or mucosal lesions were identified. There was no cervical, axillary, or inguinal lymphadenopathy. A laboratory workup consisting of serum immunoglobulins and serum protein electrophoresis was unremarkable. Tests for HIV-1 and HIV-2 as well as human T-lymphotropic virus 1 and 2 were negative. The CD4 and CD8 counts were within reference range. Histopathology of a shave biopsy revealed a dermal spindle cell proliferation arranged in short intersecting fascicles and admixed with plasma cells and occasional mitotic figures. Immunohistochemistry showed that the spindle cells stained positive for CD34, CD31, and HHV-8 (Figure 2). The lesion resolved after treatment with cryotherapy. Repeat HIV testing 3 months later was negative. No recurrence or new lesions were identified at 3-month follow-up.

Similar to the other subtypes of KS, the nonepidemic form is dependent on HHV-8 infection, which is more commonly transmitted via saliva and sexual contact.^3,4 After infecting endothelial cells, HHV-8 is believed to activate the mammalian target of rapamycin and nuclear factor κB pathways, resulting in aberrant cellular differentiation and neoangiogenesis through upregulation of vascular endothelial growth factor and basic fibroblast growth factor.^2,4 Similar to what is seen with other herpesviruses, HHV-8 infection typically is lifelong due to the virus’s ability to establish latency within human B cells and endothelial cells as well as undergo sporadic bouts of lytic reactivation during its life cycle.⁴

Nonepidemic KS resembles other variants clinically, manifesting as erythematous or violaceous, painless, nonblanchable macules, papules, and nodules.¹ Early lesions often are asymptomatic and can manifest as pigmented macules or small papules that vary from pale pink to vivid purple. Nodules also can occur and be exophytic and ulcerated with bleeding.¹ Secondary lymphoproliferative disorders including Castleman disease and lymphoma have been reported.^2,5

In contrast to other types of KS in which pulmonary or gastrointestinal tract lesions can develop with hemoptysis or hematochezia, mucocutaneous and visceral lesions rarely are reported in nonepidemic KS.³ Lymphedema, a feature associated with endemic KS, is notably absent in nonepidemic KS.^1,3

The differential diagnosis applicable to all KS subtypes includes other vascular lesions such as angiomatosis and angiosarcoma. Histopathologic analysis is critical to differentiate KS from these conditions; visual diagnosis alone has only an 80% positive predictive value for KS.⁴ The histopathologic presentation of KS is a vascular proliferation in the dermis accompanied by an increased number of vessels without an endothelial cell lining.⁴ Spindle cell proliferation also is a common feature and is considered to be the KS tumor cell. Immunostaining for HHV-8 antigen as well as for CD31 and CD34 can be used to confirm the diagnosis.⁴

The management and prognosis of KS depends on the epidemiologic subtype. Classic and nonepidemic KS generally are indolent with a good prognosis. Periodic follow-up is recommended because of an increased risk for secondary malignancy such as lymphoma. The treatment of epidemic KS is highly active antiretroviral therapy. Similarly, reduction of immunosuppression is warranted for iatrogenic KS. For all types, cutaneous lesions can be treated with local excision, cryosurgery, radiation, chemotherapy, intralesional vincristine, or a topical agent such as imiquimod or alitretinoin.⁶

The Diagnosis: Calcific Uremic Arteriolopathy

Computed tomography of the abdomen and pelvis with contrast revealed a right complex renal cyst with peripheral calcification; computed tomography of the head without contrast revealed atherosclerotic changes with calcification of the intracranial arteries, vertebral basilar arteries, and bilateral branches of the ophthalmic artery. Histopathology revealed occlusive vasculopathy with epidermal ischemic changes as well as dermal and subcutaneous vascular congestion and small thrombi. Within the subcutis, there were tiny stippled calcium deposits within very small vascular lumina (Figure). The combination of clinical and histological findings was highly suggestive of calcific uremic arteriolopathy, and the patient was transitioned to hemodialysis against a low-calcium bath to avoid hypercalcemia. Unfortunately, she developed complications related to sepsis and experienced worsening mentation. After a discussion with palliative care, the patient was transitioned to comfort measures and discharged home on hospice 1 week after the biopsy at her family’s request.

Calcific uremic arteriolopathy (also known as calciphylaxis) is a rare, life-threatening syndrome of widespread vascular calcification leading to microvascular occlusion within the dermis and subcutaneous tissues.¹ Clinically, it typically manifests as severely painful, purpuric skin lesions that evolve through phases of blistering, ulceration, and ultimately visible skin necrosis.² The pain likely is a consequence of ischemia and nociceptive activation and often may precede any visibly apparent skin lesions.³ Risk factors associated with the development of this condition include female sex; history of diabetes mellitus, obesity, rapid weight loss, or end-stage renal disease; abnormalities in calcium and phosphorus homeostasis; and vitamin K deficiency.^1,3 It is more prevalent in patients on peritoneal dialysis compared to hemodialysis.⁴

Calciphylaxis is diagnosed with combined clinical and histopathological evidence. Laboratory test abnormalities are not specific for disease; therefore, skin biopsy is the standard confirmatory test, though its practice is contentious due to the risk for nonhealing ulceration and increasing risk for infection.¹ Findings suggestive of disease include focal to diffuse calcification (intravascular, extravascular, or perieccrine), superficial fat calcium deposition, mid panniculus calcium deposition, mid panniculus vascular thrombi, and focal to diffuse angioplasia.⁵ The hallmark feature is diffuse calcification of small capillaries in adipose tissue.⁶

The mortality rate associated with this disease is high—a 6-month mortality rate of 27% to 43% has been reported from the time of diagnosis^7-9—which often is related to subsequent superimposed infections patients acquire from necrotic skin tissue.² The disease also carries high morbidity, with patients experiencing frequent hospitalizations related to pain, infections, and nonhealing wounds.⁶ There is no standard treatment, and trials have been limited to small sample sizes. A multidisciplinary treatment approach is essential to maximize outcomes, which includes wound care, risk factor modification, analgesia, and symptomatic management strategies.^1,2,6

Some pharmacologic agents have received noteworthy attention in treating calciphylaxis, including sodium thiosulfate (STS), bisphosphonates, and vitamin K supplementation.¹ The strongest evidence supporting the use of STS comes from 2 trials involving 53 and 27 dialysis patients, with complete remission in 14 (26%) and 14 (52%) patients, respectively.^10,11 However, these trials did not include control groups to compare outcomes, and mortality rates were similarly high among partial responders and nonresponders compared with patients not treated with STS. A 2018 systematic review failed to assess the efficacy of STS alone for the treatment of calciphylaxis but suggested there may be a future role for it, with 251 of 358 patients (70.1%) responding to therapy.¹²

Erythema ab igne is a cutaneous reaction related to long-term heat exposure, often from electronic devices such as laptops, heating pads, space heaters, or hot-water bottles.^13,14 Clinically, this rash appears as an erythematous, purpuric, or hyperpigmented reticular dermatosis that is below the clinical threshold to define a thermal burn.¹³ Lesions often are seen on the anterior thighs or across the abdomen.¹⁵ There usually are no long-term clinical sequelae; however, rare malignant transformation has been documented in cases of atrophy or nonhealing ulceration.¹⁶ Treatment is supportive with removal of the offending agent, but hyperpigmentation may persist for months to years.¹⁴

Livedo reticularis is a cutaneous pattern of mottled violaceous or hyperpigmented changes that often signifies underlying vascular dermal changes.¹⁷ It can be seen in various pathologic states, including vasculitis, autoimmune disease, connective tissue disease, neurologic disease, infection, or malignancy, or it can be drug induced.¹⁸ There are no pathognomonic microscopic changes, as the histology will drastically differ based on the etiology. Workup can be extensive; cues to the underlying pathology should be sought based on the patient’s history and concurrent presenting symptoms. Livedo reticularis is the most common dermatologic finding in patients with antiphospholipid syndrome, and workup should include antiphospholipid antibodies (eg, lupus anticoagulant, anticardiolipin, anti–beta-2-glycoproteins) as well as lupus testing (eg, antinuclear antibodies, anti– double-stranded DNA).¹⁹ Treatment is targeted at the underlying disease process.

Cryoglobulinemia is a disease characterized by abnormal serum immunoglobulins that precipitate at cold temperatures and is further subcategorized by the type of complexes that are deposited.²⁰ Type I represents purely monoclonal cryoglobulins, type III purely polyclonal, and type II a mixed picture. Clinical manifestations arise from excessive deposition of these proteins in the skin, joints, peripheral vasculature, and kidneys leading to purpuric skin lesions, chronic ulceration, arthralgia, and glomerulonephritis. Cutaneous findings may include erythematous to purpuric macular or papular changes with or without the presence of ulceration, infarction, or hemorrhagic crusting.²¹ Systemic disease often underlies a diagnosis, and further investigation for hepatitis C virus, connective tissue disease, and hematologic malignancies should be considered.²⁰ Treatment is targeted at underlying systemic disease, such as antiviral treatment for hepatitis or chemotherapeutic regimens for hematologic disease.²²

Polyarteritis nodosa is a systemic necrotizing vasculitis that typically involves small- to medium-sized arteries. Cutaneous manifestations often include subcutaneous nodules, livedo reticularis, and ulcerations most found on the lower extremities.²³ Systemic symptoms including fever, myalgia, arthralgia, and neuropathy often are present. Characteristic histopathology findings include inflammation and destruction of medium-sized arteries at the junctional zone of the dermis and subcutis along with microaneurysms along the vessels.²⁴ Treatment is based on the severity of disease, with localized cutaneous disease often being controlled with topical steroids and anti-inflammatory agents, while more widespread disease requires immunosuppression with systemic steroids, hydroxychloroquine, azathioprine, methotrexate, mycophenolate mofetil, or intravenous immunoglobulins.²³

The Diagnosis: Calcific Uremic Arteriolopathy

Computed tomography of the abdomen and pelvis with contrast revealed a right complex renal cyst with peripheral calcification; computed tomography of the head without contrast revealed atherosclerotic changes with calcification of the intracranial arteries, vertebral basilar arteries, and bilateral branches of the ophthalmic artery. Histopathology revealed occlusive vasculopathy with epidermal ischemic changes as well as dermal and subcutaneous vascular congestion and small thrombi. Within the subcutis, there were tiny stippled calcium deposits within very small vascular lumina (Figure). The combination of clinical and histological findings was highly suggestive of calcific uremic arteriolopathy, and the patient was transitioned to hemodialysis against a low-calcium bath to avoid hypercalcemia. Unfortunately, she developed complications related to sepsis and experienced worsening mentation. After a discussion with palliative care, the patient was transitioned to comfort measures and discharged home on hospice 1 week after the biopsy at her family’s request.

Calcific uremic arteriolopathy (also known as calciphylaxis) is a rare, life-threatening syndrome of widespread vascular calcification leading to microvascular occlusion within the dermis and subcutaneous tissues.¹ Clinically, it typically manifests as severely painful, purpuric skin lesions that evolve through phases of blistering, ulceration, and ultimately visible skin necrosis.² The pain likely is a consequence of ischemia and nociceptive activation and often may precede any visibly apparent skin lesions.³ Risk factors associated with the development of this condition include female sex; history of diabetes mellitus, obesity, rapid weight loss, or end-stage renal disease; abnormalities in calcium and phosphorus homeostasis; and vitamin K deficiency.^1,3 It is more prevalent in patients on peritoneal dialysis compared to hemodialysis.⁴

Calciphylaxis is diagnosed with combined clinical and histopathological evidence. Laboratory test abnormalities are not specific for disease; therefore, skin biopsy is the standard confirmatory test, though its practice is contentious due to the risk for nonhealing ulceration and increasing risk for infection.¹ Findings suggestive of disease include focal to diffuse calcification (intravascular, extravascular, or perieccrine), superficial fat calcium deposition, mid panniculus calcium deposition, mid panniculus vascular thrombi, and focal to diffuse angioplasia.⁵ The hallmark feature is diffuse calcification of small capillaries in adipose tissue.⁶

The mortality rate associated with this disease is high—a 6-month mortality rate of 27% to 43% has been reported from the time of diagnosis^7-9—which often is related to subsequent superimposed infections patients acquire from necrotic skin tissue.² The disease also carries high morbidity, with patients experiencing frequent hospitalizations related to pain, infections, and nonhealing wounds.⁶ There is no standard treatment, and trials have been limited to small sample sizes. A multidisciplinary treatment approach is essential to maximize outcomes, which includes wound care, risk factor modification, analgesia, and symptomatic management strategies.^1,2,6

Some pharmacologic agents have received noteworthy attention in treating calciphylaxis, including sodium thiosulfate (STS), bisphosphonates, and vitamin K supplementation.¹ The strongest evidence supporting the use of STS comes from 2 trials involving 53 and 27 dialysis patients, with complete remission in 14 (26%) and 14 (52%) patients, respectively.^10,11 However, these trials did not include control groups to compare outcomes, and mortality rates were similarly high among partial responders and nonresponders compared with patients not treated with STS. A 2018 systematic review failed to assess the efficacy of STS alone for the treatment of calciphylaxis but suggested there may be a future role for it, with 251 of 358 patients (70.1%) responding to therapy.¹²

Erythema ab igne is a cutaneous reaction related to long-term heat exposure, often from electronic devices such as laptops, heating pads, space heaters, or hot-water bottles.^13,14 Clinically, this rash appears as an erythematous, purpuric, or hyperpigmented reticular dermatosis that is below the clinical threshold to define a thermal burn.¹³ Lesions often are seen on the anterior thighs or across the abdomen.¹⁵ There usually are no long-term clinical sequelae; however, rare malignant transformation has been documented in cases of atrophy or nonhealing ulceration.¹⁶ Treatment is supportive with removal of the offending agent, but hyperpigmentation may persist for months to years.¹⁴

Livedo reticularis is a cutaneous pattern of mottled violaceous or hyperpigmented changes that often signifies underlying vascular dermal changes.¹⁷ It can be seen in various pathologic states, including vasculitis, autoimmune disease, connective tissue disease, neurologic disease, infection, or malignancy, or it can be drug induced.¹⁸ There are no pathognomonic microscopic changes, as the histology will drastically differ based on the etiology. Workup can be extensive; cues to the underlying pathology should be sought based on the patient’s history and concurrent presenting symptoms. Livedo reticularis is the most common dermatologic finding in patients with antiphospholipid syndrome, and workup should include antiphospholipid antibodies (eg, lupus anticoagulant, anticardiolipin, anti–beta-2-glycoproteins) as well as lupus testing (eg, antinuclear antibodies, anti– double-stranded DNA).¹⁹ Treatment is targeted at the underlying disease process.

Cryoglobulinemia is a disease characterized by abnormal serum immunoglobulins that precipitate at cold temperatures and is further subcategorized by the type of complexes that are deposited.²⁰ Type I represents purely monoclonal cryoglobulins, type III purely polyclonal, and type II a mixed picture. Clinical manifestations arise from excessive deposition of these proteins in the skin, joints, peripheral vasculature, and kidneys leading to purpuric skin lesions, chronic ulceration, arthralgia, and glomerulonephritis. Cutaneous findings may include erythematous to purpuric macular or papular changes with or without the presence of ulceration, infarction, or hemorrhagic crusting.²¹ Systemic disease often underlies a diagnosis, and further investigation for hepatitis C virus, connective tissue disease, and hematologic malignancies should be considered.²⁰ Treatment is targeted at underlying systemic disease, such as antiviral treatment for hepatitis or chemotherapeutic regimens for hematologic disease.²²

Polyarteritis nodosa is a systemic necrotizing vasculitis that typically involves small- to medium-sized arteries. Cutaneous manifestations often include subcutaneous nodules, livedo reticularis, and ulcerations most found on the lower extremities.²³ Systemic symptoms including fever, myalgia, arthralgia, and neuropathy often are present. Characteristic histopathology findings include inflammation and destruction of medium-sized arteries at the junctional zone of the dermis and subcutis along with microaneurysms along the vessels.²⁴ Treatment is based on the severity of disease, with localized cutaneous disease often being controlled with topical steroids and anti-inflammatory agents, while more widespread disease requires immunosuppression with systemic steroids, hydroxychloroquine, azathioprine, methotrexate, mycophenolate mofetil, or intravenous immunoglobulins.²³

The Diagnosis: Calcific Uremic Arteriolopathy

Computed tomography of the abdomen and pelvis with contrast revealed a right complex renal cyst with peripheral calcification; computed tomography of the head without contrast revealed atherosclerotic changes with calcification of the intracranial arteries, vertebral basilar arteries, and bilateral branches of the ophthalmic artery. Histopathology revealed occlusive vasculopathy with epidermal ischemic changes as well as dermal and subcutaneous vascular congestion and small thrombi. Within the subcutis, there were tiny stippled calcium deposits within very small vascular lumina (Figure). The combination of clinical and histological findings was highly suggestive of calcific uremic arteriolopathy, and the patient was transitioned to hemodialysis against a low-calcium bath to avoid hypercalcemia. Unfortunately, she developed complications related to sepsis and experienced worsening mentation. After a discussion with palliative care, the patient was transitioned to comfort measures and discharged home on hospice 1 week after the biopsy at her family’s request.

Calcific uremic arteriolopathy (also known as calciphylaxis) is a rare, life-threatening syndrome of widespread vascular calcification leading to microvascular occlusion within the dermis and subcutaneous tissues.¹ Clinically, it typically manifests as severely painful, purpuric skin lesions that evolve through phases of blistering, ulceration, and ultimately visible skin necrosis.² The pain likely is a consequence of ischemia and nociceptive activation and often may precede any visibly apparent skin lesions.³ Risk factors associated with the development of this condition include female sex; history of diabetes mellitus, obesity, rapid weight loss, or end-stage renal disease; abnormalities in calcium and phosphorus homeostasis; and vitamin K deficiency.^1,3 It is more prevalent in patients on peritoneal dialysis compared to hemodialysis.⁴

Calciphylaxis is diagnosed with combined clinical and histopathological evidence. Laboratory test abnormalities are not specific for disease; therefore, skin biopsy is the standard confirmatory test, though its practice is contentious due to the risk for nonhealing ulceration and increasing risk for infection.¹ Findings suggestive of disease include focal to diffuse calcification (intravascular, extravascular, or perieccrine), superficial fat calcium deposition, mid panniculus calcium deposition, mid panniculus vascular thrombi, and focal to diffuse angioplasia.⁵ The hallmark feature is diffuse calcification of small capillaries in adipose tissue.⁶

The mortality rate associated with this disease is high—a 6-month mortality rate of 27% to 43% has been reported from the time of diagnosis^7-9—which often is related to subsequent superimposed infections patients acquire from necrotic skin tissue.² The disease also carries high morbidity, with patients experiencing frequent hospitalizations related to pain, infections, and nonhealing wounds.⁶ There is no standard treatment, and trials have been limited to small sample sizes. A multidisciplinary treatment approach is essential to maximize outcomes, which includes wound care, risk factor modification, analgesia, and symptomatic management strategies.^1,2,6

Some pharmacologic agents have received noteworthy attention in treating calciphylaxis, including sodium thiosulfate (STS), bisphosphonates, and vitamin K supplementation.¹ The strongest evidence supporting the use of STS comes from 2 trials involving 53 and 27 dialysis patients, with complete remission in 14 (26%) and 14 (52%) patients, respectively.^10,11 However, these trials did not include control groups to compare outcomes, and mortality rates were similarly high among partial responders and nonresponders compared with patients not treated with STS. A 2018 systematic review failed to assess the efficacy of STS alone for the treatment of calciphylaxis but suggested there may be a future role for it, with 251 of 358 patients (70.1%) responding to therapy.¹²

Erythema ab igne is a cutaneous reaction related to long-term heat exposure, often from electronic devices such as laptops, heating pads, space heaters, or hot-water bottles.^13,14 Clinically, this rash appears as an erythematous, purpuric, or hyperpigmented reticular dermatosis that is below the clinical threshold to define a thermal burn.¹³ Lesions often are seen on the anterior thighs or across the abdomen.¹⁵ There usually are no long-term clinical sequelae; however, rare malignant transformation has been documented in cases of atrophy or nonhealing ulceration.¹⁶ Treatment is supportive with removal of the offending agent, but hyperpigmentation may persist for months to years.¹⁴

Livedo reticularis is a cutaneous pattern of mottled violaceous or hyperpigmented changes that often signifies underlying vascular dermal changes.¹⁷ It can be seen in various pathologic states, including vasculitis, autoimmune disease, connective tissue disease, neurologic disease, infection, or malignancy, or it can be drug induced.¹⁸ There are no pathognomonic microscopic changes, as the histology will drastically differ based on the etiology. Workup can be extensive; cues to the underlying pathology should be sought based on the patient’s history and concurrent presenting symptoms. Livedo reticularis is the most common dermatologic finding in patients with antiphospholipid syndrome, and workup should include antiphospholipid antibodies (eg, lupus anticoagulant, anticardiolipin, anti–beta-2-glycoproteins) as well as lupus testing (eg, antinuclear antibodies, anti– double-stranded DNA).¹⁹ Treatment is targeted at the underlying disease process.

Cryoglobulinemia is a disease characterized by abnormal serum immunoglobulins that precipitate at cold temperatures and is further subcategorized by the type of complexes that are deposited.²⁰ Type I represents purely monoclonal cryoglobulins, type III purely polyclonal, and type II a mixed picture. Clinical manifestations arise from excessive deposition of these proteins in the skin, joints, peripheral vasculature, and kidneys leading to purpuric skin lesions, chronic ulceration, arthralgia, and glomerulonephritis. Cutaneous findings may include erythematous to purpuric macular or papular changes with or without the presence of ulceration, infarction, or hemorrhagic crusting.²¹ Systemic disease often underlies a diagnosis, and further investigation for hepatitis C virus, connective tissue disease, and hematologic malignancies should be considered.²⁰ Treatment is targeted at underlying systemic disease, such as antiviral treatment for hepatitis or chemotherapeutic regimens for hematologic disease.²²

Polyarteritis nodosa is a systemic necrotizing vasculitis that typically involves small- to medium-sized arteries. Cutaneous manifestations often include subcutaneous nodules, livedo reticularis, and ulcerations most found on the lower extremities.²³ Systemic symptoms including fever, myalgia, arthralgia, and neuropathy often are present. Characteristic histopathology findings include inflammation and destruction of medium-sized arteries at the junctional zone of the dermis and subcutis along with microaneurysms along the vessels.²⁴ Treatment is based on the severity of disease, with localized cutaneous disease often being controlled with topical steroids and anti-inflammatory agents, while more widespread disease requires immunosuppression with systemic steroids, hydroxychloroquine, azathioprine, methotrexate, mycophenolate mofetil, or intravenous immunoglobulins.²³

The Diagnosis: Giant Apocrine Hidrocystoma

Histopathology of the noduloplaque revealed an unremarkable epidermis with multilocular cystic spaces centered in the dermis. The cysts had a double-lined epithelium with inner columnar to cuboidal cells and outer myoepithelial cells (bottom quiz image). Columnar cells showing decapitation secretion could be appreciated at places indicating apocrine secretion (Figure). A final diagnosis of apocrine hidrocystoma was made.

Hidrocystomas are rare, benign, cystic lesions derived either from apocrine or eccrine glands.¹ Apocrine hidrocystoma usually manifests as asymptomatic, solitary, dome-shaped papules or nodules with a predilection for the head and neck region. Hidrocystomas can vary from flesh colored to blue, brown, or black. Pigmentation in hidrocystoma is seen in 5% to 80% of cases and is attributed to the Tyndall effect.¹ The tumor usually is less than 20 mm in diameter; larger lesions are termed giant apocrine hidrocystoma.² Apocrine hidrocystoma manifesting with multiple lesions and a size greater than 10 mm, as seen in our case, is uncommon.

Zaballos et al³ described dermoscopy of apocrine hidrocystoma in 22 patients. Hallmark dermoscopic findings were the presence of a homogeneous flesh-colored, yellowish, blue to pinkish-blue area involving the entire lesion with arborizing vessels and whitish structures.³ Similar dermoscopic findings were present in our patient. The homogeneous area histologically correlates to the multiloculated cysts located in the dermis. The exact reason for white structures is unknown; however, their visualization in apocrine hidrocystoma could be attributed to the alternation in collagen orientation secondary to the presence of large or multiple cysts in the dermis.

The presence of shiny white dots arranged in a square resembling a four-leaf clover (also known as white rosettes) was a unique dermoscopic finding in our patient. These rosettes can be appreciated only with polarized dermoscopy, and they have been described in actinic keratosis, seborrheic keratosis, squamous cell carcinoma, and basal cell carcinoma.⁴ The exact morphologic correlate of white rosettes is unknown but is postulated to be secondary to material inside adnexal openings in small rosettes and concentric perifollicular fibrosis in larger rosettes.⁴ In our patient, we believe the white rosettes can be attributed to the accumulated secretions in the dermal glands, which also were seen via histopathology. Dermoscopy also revealed increased peripheral, brown, networklike pigmentation, which was unique and could be secondary to the patient’s darker skin phenotype.

Differential diagnoses of apocrine hidrocystoma include both melanocytic and nonmelanocytic conditions such as epidermal cyst, nodular melanoma, nodular hidradenoma, syringoma, blue nevus, pilomatricoma, eccrine poroma, nodular Kaposi sarcoma, and venous lake.1 Histopathology showing large unilocular or multilocular dermal cysts with double lining comprising outer myoepithelial cells and inner columnar or cuboidal cell with decapitation secretion is paramount in confirming the diagnosis of apocrine hidrocystoma.

Dermoscopy can act as a valuable noninvasive modality in differentiating apocrine hidrocystoma from its melanocytic and nonmelanocytic differential diagnoses (Table).^5-8 In our patient, the presence of a homogeneous pink to bluish area involving the entire lesion, linear branched vessels, and whitish structures on dermoscopy pointed to the diagnosis of apocrine hidrocystoma, which was further confirmed by characteristic histopathologic findings.

The treatment of apocrine hidrocystoma includes surgical excision for solitary lesions, with electrodesiccation and curettage, chemical cautery, and CO₂ laser ablation employed for multiple lesions.¹ Our patient was scheduled for CO₂ laser ablation, considering the multiple lesions and size of the apocrine hidrocystoma but was subsequently lost to follow-up.

The Diagnosis: Giant Apocrine Hidrocystoma

Histopathology of the noduloplaque revealed an unremarkable epidermis with multilocular cystic spaces centered in the dermis. The cysts had a double-lined epithelium with inner columnar to cuboidal cells and outer myoepithelial cells (bottom quiz image). Columnar cells showing decapitation secretion could be appreciated at places indicating apocrine secretion (Figure). A final diagnosis of apocrine hidrocystoma was made.

Hidrocystomas are rare, benign, cystic lesions derived either from apocrine or eccrine glands.¹ Apocrine hidrocystoma usually manifests as asymptomatic, solitary, dome-shaped papules or nodules with a predilection for the head and neck region. Hidrocystomas can vary from flesh colored to blue, brown, or black. Pigmentation in hidrocystoma is seen in 5% to 80% of cases and is attributed to the Tyndall effect.¹ The tumor usually is less than 20 mm in diameter; larger lesions are termed giant apocrine hidrocystoma.² Apocrine hidrocystoma manifesting with multiple lesions and a size greater than 10 mm, as seen in our case, is uncommon.

Zaballos et al³ described dermoscopy of apocrine hidrocystoma in 22 patients. Hallmark dermoscopic findings were the presence of a homogeneous flesh-colored, yellowish, blue to pinkish-blue area involving the entire lesion with arborizing vessels and whitish structures.³ Similar dermoscopic findings were present in our patient. The homogeneous area histologically correlates to the multiloculated cysts located in the dermis. The exact reason for white structures is unknown; however, their visualization in apocrine hidrocystoma could be attributed to the alternation in collagen orientation secondary to the presence of large or multiple cysts in the dermis.

The presence of shiny white dots arranged in a square resembling a four-leaf clover (also known as white rosettes) was a unique dermoscopic finding in our patient. These rosettes can be appreciated only with polarized dermoscopy, and they have been described in actinic keratosis, seborrheic keratosis, squamous cell carcinoma, and basal cell carcinoma.⁴ The exact morphologic correlate of white rosettes is unknown but is postulated to be secondary to material inside adnexal openings in small rosettes and concentric perifollicular fibrosis in larger rosettes.⁴ In our patient, we believe the white rosettes can be attributed to the accumulated secretions in the dermal glands, which also were seen via histopathology. Dermoscopy also revealed increased peripheral, brown, networklike pigmentation, which was unique and could be secondary to the patient’s darker skin phenotype.

Differential diagnoses of apocrine hidrocystoma include both melanocytic and nonmelanocytic conditions such as epidermal cyst, nodular melanoma, nodular hidradenoma, syringoma, blue nevus, pilomatricoma, eccrine poroma, nodular Kaposi sarcoma, and venous lake.1 Histopathology showing large unilocular or multilocular dermal cysts with double lining comprising outer myoepithelial cells and inner columnar or cuboidal cell with decapitation secretion is paramount in confirming the diagnosis of apocrine hidrocystoma.

Dermoscopy can act as a valuable noninvasive modality in differentiating apocrine hidrocystoma from its melanocytic and nonmelanocytic differential diagnoses (Table).^5-8 In our patient, the presence of a homogeneous pink to bluish area involving the entire lesion, linear branched vessels, and whitish structures on dermoscopy pointed to the diagnosis of apocrine hidrocystoma, which was further confirmed by characteristic histopathologic findings.

The treatment of apocrine hidrocystoma includes surgical excision for solitary lesions, with electrodesiccation and curettage, chemical cautery, and CO₂ laser ablation employed for multiple lesions.¹ Our patient was scheduled for CO₂ laser ablation, considering the multiple lesions and size of the apocrine hidrocystoma but was subsequently lost to follow-up.

The Diagnosis: Giant Apocrine Hidrocystoma

Histopathology of the noduloplaque revealed an unremarkable epidermis with multilocular cystic spaces centered in the dermis. The cysts had a double-lined epithelium with inner columnar to cuboidal cells and outer myoepithelial cells (bottom quiz image). Columnar cells showing decapitation secretion could be appreciated at places indicating apocrine secretion (Figure). A final diagnosis of apocrine hidrocystoma was made.

Hidrocystomas are rare, benign, cystic lesions derived either from apocrine or eccrine glands.¹ Apocrine hidrocystoma usually manifests as asymptomatic, solitary, dome-shaped papules or nodules with a predilection for the head and neck region. Hidrocystomas can vary from flesh colored to blue, brown, or black. Pigmentation in hidrocystoma is seen in 5% to 80% of cases and is attributed to the Tyndall effect.¹ The tumor usually is less than 20 mm in diameter; larger lesions are termed giant apocrine hidrocystoma.² Apocrine hidrocystoma manifesting with multiple lesions and a size greater than 10 mm, as seen in our case, is uncommon.

Zaballos et al³ described dermoscopy of apocrine hidrocystoma in 22 patients. Hallmark dermoscopic findings were the presence of a homogeneous flesh-colored, yellowish, blue to pinkish-blue area involving the entire lesion with arborizing vessels and whitish structures.³ Similar dermoscopic findings were present in our patient. The homogeneous area histologically correlates to the multiloculated cysts located in the dermis. The exact reason for white structures is unknown; however, their visualization in apocrine hidrocystoma could be attributed to the alternation in collagen orientation secondary to the presence of large or multiple cysts in the dermis.

The presence of shiny white dots arranged in a square resembling a four-leaf clover (also known as white rosettes) was a unique dermoscopic finding in our patient. These rosettes can be appreciated only with polarized dermoscopy, and they have been described in actinic keratosis, seborrheic keratosis, squamous cell carcinoma, and basal cell carcinoma.⁴ The exact morphologic correlate of white rosettes is unknown but is postulated to be secondary to material inside adnexal openings in small rosettes and concentric perifollicular fibrosis in larger rosettes.⁴ In our patient, we believe the white rosettes can be attributed to the accumulated secretions in the dermal glands, which also were seen via histopathology. Dermoscopy also revealed increased peripheral, brown, networklike pigmentation, which was unique and could be secondary to the patient’s darker skin phenotype.

Differential diagnoses of apocrine hidrocystoma include both melanocytic and nonmelanocytic conditions such as epidermal cyst, nodular melanoma, nodular hidradenoma, syringoma, blue nevus, pilomatricoma, eccrine poroma, nodular Kaposi sarcoma, and venous lake.1 Histopathology showing large unilocular or multilocular dermal cysts with double lining comprising outer myoepithelial cells and inner columnar or cuboidal cell with decapitation secretion is paramount in confirming the diagnosis of apocrine hidrocystoma.

Dermoscopy can act as a valuable noninvasive modality in differentiating apocrine hidrocystoma from its melanocytic and nonmelanocytic differential diagnoses (Table).^5-8 In our patient, the presence of a homogeneous pink to bluish area involving the entire lesion, linear branched vessels, and whitish structures on dermoscopy pointed to the diagnosis of apocrine hidrocystoma, which was further confirmed by characteristic histopathologic findings.

The treatment of apocrine hidrocystoma includes surgical excision for solitary lesions, with electrodesiccation and curettage, chemical cautery, and CO₂ laser ablation employed for multiple lesions.¹ Our patient was scheduled for CO₂ laser ablation, considering the multiple lesions and size of the apocrine hidrocystoma but was subsequently lost to follow-up.

The Diagnosis: Granuloma Annulare

The biopsies revealed palisading granulomatous dermatitis consistent with granuloma annulare (GA). This diagnosis was supported by the clinical presentation and histopathologic findings. Although the pathogenesis of GA is unclear, it is a benign, self-limiting condition. Primarily affected sites include the trunk and forearms. Generalized GA (or GA with ≥10 lesions) may warrant workup for malignancy, as it may represent a paraneoplastic process.¹ Histopathology reveals granulomas comprising a dermal lymphohistiocytic infiltrate as well as central mucin and nuclear debris. There are a few histologic subtypes of GA, including palisading and interstitial, which refer to the distribution of the histiocytic infiltrate.^2,3 This case—with palisading histiocytes lining the collection of necrobiosis and mucin (bottom quiz image)—features palisading GA. Notably, GA exhibits central rather than diffuse mucin.⁴

Erythema gyratum repens is a paraneoplastic arcuate erythema that manifests as erythematous figurate, gyrate, or annular plaques exhibiting a trailing scale. Clinically, erythema gyratum repens spreads rapidly—as quickly as 1 cm/d—and can be extensive (as in this case). Histopathology ruled out this diagnosis in our patient. Nonspecific findings of acanthosis, parakeratosis, and superficial spongiosis can be found in erythema gyratum repens. A superficial and deep perivascular lymphohistiocytic infiltrate may be seen in figurate erythemas (Figure 1).⁵ Unlike GA, this infiltrate does not form granulomas, is more superficial, and does not contain mucin.

Histopathology also can help establish the diagnosis of leprosy and its specific subtype, as leprosy exists on a spectrum from tuberculoid to lepromatous, with a great deal of overlap in between.⁶ Lepromatous leprosy has many cutaneous clinical presentations but typically manifests as erythematous papules or nodules. It is multibacillary, and these mycobacteria form clumps known as globi that can be seen on Fite stain.⁷ In lepromatous leprosy, there is a characteristic dense lymphohistiocytic infiltrate (Figure 2) above which a Grenz zone can be seen.^4,8 There are no well-formed granulomas in lepromatous leprosy, unlike in tuberculoid leprosy, which is paucibacillary and creates a granulomatous response surrounding nerves and adnexal structures.⁶

Mycosis fungoides (MF) is the most common cutaneous lymphoma. There are patch, plaque, and tumor stages of MF, each of which exhibits various histopathologic findings.⁹ In early patch-stage MF, lymphocytes have perinuclear clearing, and the degree of lymphocytic infiltrate is out of proportion to the spongiosis present. Epidermotropism and Pautrier microabscesses often are present in the epidermis (Figure 3). In the plaque stage, there is a denser lymphoid infiltrate in a lichenoid pattern with epidermotropism and Pautrier microabscesses. The tumor stage shows a dense dermal lymphoid infiltrate with more atypia and typically a lack of epidermotropism. Rarely, MF can exhibit a granulomatous variant in which epithelioid histiocytes collect to form granulomas along with atypical lymphocytes.¹⁰

The diagnosis of cutaneous sarcoidosis requires clinicopathologic corroboration. Histopathology demonstrates epithelioid histiocytes forming noncaseating granulomas with little to no lymphocytic infiltrate (Figure 4). There typically is no necrosis or necrobiosis as there is in GA. The diagnosis of sarcoidosis can be challenging histopathologically, and stains should be used to rule out infectious processes.⁴ Asteroid bodies— star-shaped eosinophilic inclusions within giant cells—may be present but are nonspecific for sarcoidosis.¹¹ Schaumann bodies—inclusions of calcifications within giant cells—also may be present and can aid in diagnosis.¹²

The Diagnosis: Granuloma Annulare

The biopsies revealed palisading granulomatous dermatitis consistent with granuloma annulare (GA). This diagnosis was supported by the clinical presentation and histopathologic findings. Although the pathogenesis of GA is unclear, it is a benign, self-limiting condition. Primarily affected sites include the trunk and forearms. Generalized GA (or GA with ≥10 lesions) may warrant workup for malignancy, as it may represent a paraneoplastic process.¹ Histopathology reveals granulomas comprising a dermal lymphohistiocytic infiltrate as well as central mucin and nuclear debris. There are a few histologic subtypes of GA, including palisading and interstitial, which refer to the distribution of the histiocytic infiltrate.^2,3 This case—with palisading histiocytes lining the collection of necrobiosis and mucin (bottom quiz image)—features palisading GA. Notably, GA exhibits central rather than diffuse mucin.⁴

Erythema gyratum repens is a paraneoplastic arcuate erythema that manifests as erythematous figurate, gyrate, or annular plaques exhibiting a trailing scale. Clinically, erythema gyratum repens spreads rapidly—as quickly as 1 cm/d—and can be extensive (as in this case). Histopathology ruled out this diagnosis in our patient. Nonspecific findings of acanthosis, parakeratosis, and superficial spongiosis can be found in erythema gyratum repens. A superficial and deep perivascular lymphohistiocytic infiltrate may be seen in figurate erythemas (Figure 1).⁵ Unlike GA, this infiltrate does not form granulomas, is more superficial, and does not contain mucin.

Histopathology also can help establish the diagnosis of leprosy and its specific subtype, as leprosy exists on a spectrum from tuberculoid to lepromatous, with a great deal of overlap in between.⁶ Lepromatous leprosy has many cutaneous clinical presentations but typically manifests as erythematous papules or nodules. It is multibacillary, and these mycobacteria form clumps known as globi that can be seen on Fite stain.⁷ In lepromatous leprosy, there is a characteristic dense lymphohistiocytic infiltrate (Figure 2) above which a Grenz zone can be seen.^4,8 There are no well-formed granulomas in lepromatous leprosy, unlike in tuberculoid leprosy, which is paucibacillary and creates a granulomatous response surrounding nerves and adnexal structures.⁶

Mycosis fungoides (MF) is the most common cutaneous lymphoma. There are patch, plaque, and tumor stages of MF, each of which exhibits various histopathologic findings.⁹ In early patch-stage MF, lymphocytes have perinuclear clearing, and the degree of lymphocytic infiltrate is out of proportion to the spongiosis present. Epidermotropism and Pautrier microabscesses often are present in the epidermis (Figure 3). In the plaque stage, there is a denser lymphoid infiltrate in a lichenoid pattern with epidermotropism and Pautrier microabscesses. The tumor stage shows a dense dermal lymphoid infiltrate with more atypia and typically a lack of epidermotropism. Rarely, MF can exhibit a granulomatous variant in which epithelioid histiocytes collect to form granulomas along with atypical lymphocytes.¹⁰

The diagnosis of cutaneous sarcoidosis requires clinicopathologic corroboration. Histopathology demonstrates epithelioid histiocytes forming noncaseating granulomas with little to no lymphocytic infiltrate (Figure 4). There typically is no necrosis or necrobiosis as there is in GA. The diagnosis of sarcoidosis can be challenging histopathologically, and stains should be used to rule out infectious processes.⁴ Asteroid bodies— star-shaped eosinophilic inclusions within giant cells—may be present but are nonspecific for sarcoidosis.¹¹ Schaumann bodies—inclusions of calcifications within giant cells—also may be present and can aid in diagnosis.¹²

The Diagnosis: Granuloma Annulare

The biopsies revealed palisading granulomatous dermatitis consistent with granuloma annulare (GA). This diagnosis was supported by the clinical presentation and histopathologic findings. Although the pathogenesis of GA is unclear, it is a benign, self-limiting condition. Primarily affected sites include the trunk and forearms. Generalized GA (or GA with ≥10 lesions) may warrant workup for malignancy, as it may represent a paraneoplastic process.¹ Histopathology reveals granulomas comprising a dermal lymphohistiocytic infiltrate as well as central mucin and nuclear debris. There are a few histologic subtypes of GA, including palisading and interstitial, which refer to the distribution of the histiocytic infiltrate.^2,3 This case—with palisading histiocytes lining the collection of necrobiosis and mucin (bottom quiz image)—features palisading GA. Notably, GA exhibits central rather than diffuse mucin.⁴

Erythema gyratum repens is a paraneoplastic arcuate erythema that manifests as erythematous figurate, gyrate, or annular plaques exhibiting a trailing scale. Clinically, erythema gyratum repens spreads rapidly—as quickly as 1 cm/d—and can be extensive (as in this case). Histopathology ruled out this diagnosis in our patient. Nonspecific findings of acanthosis, parakeratosis, and superficial spongiosis can be found in erythema gyratum repens. A superficial and deep perivascular lymphohistiocytic infiltrate may be seen in figurate erythemas (Figure 1).⁵ Unlike GA, this infiltrate does not form granulomas, is more superficial, and does not contain mucin.

Histopathology also can help establish the diagnosis of leprosy and its specific subtype, as leprosy exists on a spectrum from tuberculoid to lepromatous, with a great deal of overlap in between.⁶ Lepromatous leprosy has many cutaneous clinical presentations but typically manifests as erythematous papules or nodules. It is multibacillary, and these mycobacteria form clumps known as globi that can be seen on Fite stain.⁷ In lepromatous leprosy, there is a characteristic dense lymphohistiocytic infiltrate (Figure 2) above which a Grenz zone can be seen.^4,8 There are no well-formed granulomas in lepromatous leprosy, unlike in tuberculoid leprosy, which is paucibacillary and creates a granulomatous response surrounding nerves and adnexal structures.⁶

Mycosis fungoides (MF) is the most common cutaneous lymphoma. There are patch, plaque, and tumor stages of MF, each of which exhibits various histopathologic findings.⁹ In early patch-stage MF, lymphocytes have perinuclear clearing, and the degree of lymphocytic infiltrate is out of proportion to the spongiosis present. Epidermotropism and Pautrier microabscesses often are present in the epidermis (Figure 3). In the plaque stage, there is a denser lymphoid infiltrate in a lichenoid pattern with epidermotropism and Pautrier microabscesses. The tumor stage shows a dense dermal lymphoid infiltrate with more atypia and typically a lack of epidermotropism. Rarely, MF can exhibit a granulomatous variant in which epithelioid histiocytes collect to form granulomas along with atypical lymphocytes.¹⁰

The diagnosis of cutaneous sarcoidosis requires clinicopathologic corroboration. Histopathology demonstrates epithelioid histiocytes forming noncaseating granulomas with little to no lymphocytic infiltrate (Figure 4). There typically is no necrosis or necrobiosis as there is in GA. The diagnosis of sarcoidosis can be challenging histopathologically, and stains should be used to rule out infectious processes.⁴ Asteroid bodies— star-shaped eosinophilic inclusions within giant cells—may be present but are nonspecific for sarcoidosis.¹¹ Schaumann bodies—inclusions of calcifications within giant cells—also may be present and can aid in diagnosis.¹²

Practice Gap

Punch biopsies are utilized frequently by dermatologists to aid in the diagnosis of various skin diseases.¹ When performing a punch biopsy, dermatologists are taught to use either forceps or skin hooks in addition to scissors to extract the tissue from the skin.² However, the use of these sterile instruments for a simple biopsy adds extra costs to the procedure. Herein, a cheaper and often faster method of obtaining the specimen from the patient is described.

The Technique

A 3- or 4-mm disposable punch biopsy tool is employed for this method. After locally anesthetizing the skin, the skin is punched to a subcutaneous depth utilizing the full length of the blade and a little extra pressure is applied downward while stretching the skin around (Figure, A). This may be helpful to dislodge the punch specimen from the surrounding skin. The specimen now can be easily removed by gently grasping it with the thumb and index finger (Figure, B and C). It then can be transferred immediately to the formalin container.

Practice Implications

This technique saves time as well as financial and environmental costs associated with the use of sterile instruments. An additional advantage to this simple method is avoiding specimen crush injuries, which are common when using forceps. This solution works in most cases but may not be suitable for certain special anatomic locations such as the scalp, nose, and ears.

Practice Gap

Punch biopsies are utilized frequently by dermatologists to aid in the diagnosis of various skin diseases.¹ When performing a punch biopsy, dermatologists are taught to use either forceps or skin hooks in addition to scissors to extract the tissue from the skin.² However, the use of these sterile instruments for a simple biopsy adds extra costs to the procedure. Herein, a cheaper and often faster method of obtaining the specimen from the patient is described.

The Technique

A 3- or 4-mm disposable punch biopsy tool is employed for this method. After locally anesthetizing the skin, the skin is punched to a subcutaneous depth utilizing the full length of the blade and a little extra pressure is applied downward while stretching the skin around (Figure, A). This may be helpful to dislodge the punch specimen from the surrounding skin. The specimen now can be easily removed by gently grasping it with the thumb and index finger (Figure, B and C). It then can be transferred immediately to the formalin container.

Practice Implications

This technique saves time as well as financial and environmental costs associated with the use of sterile instruments. An additional advantage to this simple method is avoiding specimen crush injuries, which are common when using forceps. This solution works in most cases but may not be suitable for certain special anatomic locations such as the scalp, nose, and ears.

Practice Gap

Punch biopsies are utilized frequently by dermatologists to aid in the diagnosis of various skin diseases.¹ When performing a punch biopsy, dermatologists are taught to use either forceps or skin hooks in addition to scissors to extract the tissue from the skin.² However, the use of these sterile instruments for a simple biopsy adds extra costs to the procedure. Herein, a cheaper and often faster method of obtaining the specimen from the patient is described.

The Technique

A 3- or 4-mm disposable punch biopsy tool is employed for this method. After locally anesthetizing the skin, the skin is punched to a subcutaneous depth utilizing the full length of the blade and a little extra pressure is applied downward while stretching the skin around (Figure, A). This may be helpful to dislodge the punch specimen from the surrounding skin. The specimen now can be easily removed by gently grasping it with the thumb and index finger (Figure, B and C). It then can be transferred immediately to the formalin container.

Practice Implications

This technique saves time as well as financial and environmental costs associated with the use of sterile instruments. An additional advantage to this simple method is avoiding specimen crush injuries, which are common when using forceps. This solution works in most cases but may not be suitable for certain special anatomic locations such as the scalp, nose, and ears.

The Diagnosis: Superior Vena Cava Syndrome

Computed tomography angiography of the chest confirmed a diagnosis of superior vena cava (SVC) syndrome due to external pressure of the indwelling catheter. Upon diagnosis, the left indwelling catheter was removed. Further testing to assess for a potential pulmonary embolism was negative. Resolution of the ectatic spider veins and patientreported intermittent facial swelling was achieved after catheter removal.

Superior vena cava syndrome occurs when the SVC is occluded due to extrinsic pressure or thrombosis. Although classically thought to be due to underlying bronchogenic carcinomas, all pathologies that cause compression of the SVC also can lead to vessel occlusion.¹ Superior vena cava syndrome initially can be detected on physical examination. The most prominent skin finding includes diffusely dilated blood vessels on the central chest wall, which indicate the presence of collateral blood vessels.¹ Imaging studies such as abdominal computed tomography can provide information on the etiology of the condition but are not required for diagnosis. Given the high correlation of SVC syndrome with underlying lung and mediastinal carcinomas, imaging was warranted in our patient. Imaging also can distinguish if the condition is due to external pressure or thrombosis.² For SVC syndrome due to thrombosis, endovascular therapy is first-line management; however, mechanical thrombectomy may be preferred in patients with absolute contraindication to thrombolytic agents.³ In the setting of increased external pressure on the SVC, treatment includes the removal of the source of pressure.⁴

In a case series including 78 patients, ports and indwelling catheters accounted for 71% of benign SVC cases.⁵ Our patient’s SVC syndrome most likely was due to the indwelling catheter pressing on the SVC. The goal of treatment is to address the underlying cause—whether it be pressure or thrombosis. In the setting of increased external pressure, treatment includes removal of the source of pressure from the SVC.⁴

Other differential diagnoses to consider for newonset ectatic vessels on the chest wall include generalized essential telangiectasia, scleroderma, poikiloderma vasculare atrophicans, and caput medusae. Generalized essential telangiectasia is characterized by red or pink dilated capillary blood vessels in a branch or lacelike pattern predominantly on the lower limbs. The eruption primarily is asymptomatic, though tingling or numbness may be reported.⁶ The diagnosis can be made with a punch biopsy, with histopathology showing dilated vessels in the dermis.⁷

Scleroderma is a connective tissue fibrosis disorder with variable clinical presentations. The systemic sclerosis subset can be divided into localized systemic sclerosis and diffuse systemic sclerosis. Physical examination reveals cutaneous sclerosis in various areas of the body. Localized systemic sclerosis includes sclerosis of the fingers and face, while diffuse systemic sclerosis is notable for progression to the arms, legs, and trunk.⁸ In addition to sclerosis, diffuse telangiectases also can be observed. Systemic sclerosis is a clinical diagnosis based on physical examination and laboratory studies to identify antibodies such as antinuclear antibodies.

Poikiloderma vasculare atrophicans is a variant of cutaneous T-cell lymphoma. The initial presentation is characterized by plaques of hypopigmentation and hyperpigmentation with atrophy and telangiectases. The lesions may be asymptomatic or mildly pruritic and classically involve the trunk and flexural areas.⁹ The diagnosis is made with skin biopsy and immunohistochemical studies, with findings reflective of mycosis fungoides.

Caput medusae (palm tree sign) is a cardinal feature of portal hypertension characterized by grossly dilated and engorged periumbilical veins. To shunt blood from the portal venous system, cutaneous collateral veins between the umbilical veins and abdominal wall veins are used, resulting in the appearance of engorged veins in the anterior abdominal wall.¹⁰ The diagnosis can be made with abdominal ultrasonography showing the direction of blood flow through abdominal vessels.

The Diagnosis: Superior Vena Cava Syndrome

Computed tomography angiography of the chest confirmed a diagnosis of superior vena cava (SVC) syndrome due to external pressure of the indwelling catheter. Upon diagnosis, the left indwelling catheter was removed. Further testing to assess for a potential pulmonary embolism was negative. Resolution of the ectatic spider veins and patientreported intermittent facial swelling was achieved after catheter removal.

Superior vena cava syndrome occurs when the SVC is occluded due to extrinsic pressure or thrombosis. Although classically thought to be due to underlying bronchogenic carcinomas, all pathologies that cause compression of the SVC also can lead to vessel occlusion.¹ Superior vena cava syndrome initially can be detected on physical examination. The most prominent skin finding includes diffusely dilated blood vessels on the central chest wall, which indicate the presence of collateral blood vessels.¹ Imaging studies such as abdominal computed tomography can provide information on the etiology of the condition but are not required for diagnosis. Given the high correlation of SVC syndrome with underlying lung and mediastinal carcinomas, imaging was warranted in our patient. Imaging also can distinguish if the condition is due to external pressure or thrombosis.² For SVC syndrome due to thrombosis, endovascular therapy is first-line management; however, mechanical thrombectomy may be preferred in patients with absolute contraindication to thrombolytic agents.³ In the setting of increased external pressure on the SVC, treatment includes the removal of the source of pressure.⁴

In a case series including 78 patients, ports and indwelling catheters accounted for 71% of benign SVC cases.⁵ Our patient’s SVC syndrome most likely was due to the indwelling catheter pressing on the SVC. The goal of treatment is to address the underlying cause—whether it be pressure or thrombosis. In the setting of increased external pressure, treatment includes removal of the source of pressure from the SVC.⁴

Other differential diagnoses to consider for newonset ectatic vessels on the chest wall include generalized essential telangiectasia, scleroderma, poikiloderma vasculare atrophicans, and caput medusae. Generalized essential telangiectasia is characterized by red or pink dilated capillary blood vessels in a branch or lacelike pattern predominantly on the lower limbs. The eruption primarily is asymptomatic, though tingling or numbness may be reported.⁶ The diagnosis can be made with a punch biopsy, with histopathology showing dilated vessels in the dermis.⁷

Scleroderma is a connective tissue fibrosis disorder with variable clinical presentations. The systemic sclerosis subset can be divided into localized systemic sclerosis and diffuse systemic sclerosis. Physical examination reveals cutaneous sclerosis in various areas of the body. Localized systemic sclerosis includes sclerosis of the fingers and face, while diffuse systemic sclerosis is notable for progression to the arms, legs, and trunk.⁸ In addition to sclerosis, diffuse telangiectases also can be observed. Systemic sclerosis is a clinical diagnosis based on physical examination and laboratory studies to identify antibodies such as antinuclear antibodies.

Poikiloderma vasculare atrophicans is a variant of cutaneous T-cell lymphoma. The initial presentation is characterized by plaques of hypopigmentation and hyperpigmentation with atrophy and telangiectases. The lesions may be asymptomatic or mildly pruritic and classically involve the trunk and flexural areas.⁹ The diagnosis is made with skin biopsy and immunohistochemical studies, with findings reflective of mycosis fungoides.

Caput medusae (palm tree sign) is a cardinal feature of portal hypertension characterized by grossly dilated and engorged periumbilical veins. To shunt blood from the portal venous system, cutaneous collateral veins between the umbilical veins and abdominal wall veins are used, resulting in the appearance of engorged veins in the anterior abdominal wall.¹⁰ The diagnosis can be made with abdominal ultrasonography showing the direction of blood flow through abdominal vessels.

The Diagnosis: Superior Vena Cava Syndrome

Computed tomography angiography of the chest confirmed a diagnosis of superior vena cava (SVC) syndrome due to external pressure of the indwelling catheter. Upon diagnosis, the left indwelling catheter was removed. Further testing to assess for a potential pulmonary embolism was negative. Resolution of the ectatic spider veins and patientreported intermittent facial swelling was achieved after catheter removal.

Superior vena cava syndrome occurs when the SVC is occluded due to extrinsic pressure or thrombosis. Although classically thought to be due to underlying bronchogenic carcinomas, all pathologies that cause compression of the SVC also can lead to vessel occlusion.¹ Superior vena cava syndrome initially can be detected on physical examination. The most prominent skin finding includes diffusely dilated blood vessels on the central chest wall, which indicate the presence of collateral blood vessels.¹ Imaging studies such as abdominal computed tomography can provide information on the etiology of the condition but are not required for diagnosis. Given the high correlation of SVC syndrome with underlying lung and mediastinal carcinomas, imaging was warranted in our patient. Imaging also can distinguish if the condition is due to external pressure or thrombosis.² For SVC syndrome due to thrombosis, endovascular therapy is first-line management; however, mechanical thrombectomy may be preferred in patients with absolute contraindication to thrombolytic agents.³ In the setting of increased external pressure on the SVC, treatment includes the removal of the source of pressure.⁴

In a case series including 78 patients, ports and indwelling catheters accounted for 71% of benign SVC cases.⁵ Our patient’s SVC syndrome most likely was due to the indwelling catheter pressing on the SVC. The goal of treatment is to address the underlying cause—whether it be pressure or thrombosis. In the setting of increased external pressure, treatment includes removal of the source of pressure from the SVC.⁴

Other differential diagnoses to consider for newonset ectatic vessels on the chest wall include generalized essential telangiectasia, scleroderma, poikiloderma vasculare atrophicans, and caput medusae. Generalized essential telangiectasia is characterized by red or pink dilated capillary blood vessels in a branch or lacelike pattern predominantly on the lower limbs. The eruption primarily is asymptomatic, though tingling or numbness may be reported.⁶ The diagnosis can be made with a punch biopsy, with histopathology showing dilated vessels in the dermis.⁷

Scleroderma is a connective tissue fibrosis disorder with variable clinical presentations. The systemic sclerosis subset can be divided into localized systemic sclerosis and diffuse systemic sclerosis. Physical examination reveals cutaneous sclerosis in various areas of the body. Localized systemic sclerosis includes sclerosis of the fingers and face, while diffuse systemic sclerosis is notable for progression to the arms, legs, and trunk.⁸ In addition to sclerosis, diffuse telangiectases also can be observed. Systemic sclerosis is a clinical diagnosis based on physical examination and laboratory studies to identify antibodies such as antinuclear antibodies.

Poikiloderma vasculare atrophicans is a variant of cutaneous T-cell lymphoma. The initial presentation is characterized by plaques of hypopigmentation and hyperpigmentation with atrophy and telangiectases. The lesions may be asymptomatic or mildly pruritic and classically involve the trunk and flexural areas.⁹ The diagnosis is made with skin biopsy and immunohistochemical studies, with findings reflective of mycosis fungoides.

Caput medusae (palm tree sign) is a cardinal feature of portal hypertension characterized by grossly dilated and engorged periumbilical veins. To shunt blood from the portal venous system, cutaneous collateral veins between the umbilical veins and abdominal wall veins are used, resulting in the appearance of engorged veins in the anterior abdominal wall.¹⁰ The diagnosis can be made with abdominal ultrasonography showing the direction of blood flow through abdominal vessels.

The Diagnosis: Cutaneous Rosai-Dorfman Disease

Rosai-Dorfman disease is a rare benign non- Langerhans cell histiocytopathy that can manifest initially with lymph node involvement—classically, massive painless cervical lymphadenopathy.¹ Cutaneous Rosai-Dorfman disease (CRDD) is a variant that can be associated with lymph node and internal involvement, but more than 80% of cases lack extracutaneous involvement.^2,3 In cases with extracutaneous involvement, lymph node disease is most frequent.3 Cutaneous Rosai-Dorfman disease unassociated with extracutaneous disease is a benign self-limiting histiocytopathy that manifests as painless red-brown, yellow, or fleshcolored nodules, plaques, or papules that may become tender or ulcerated.⁴

Cutaneous Rosai-Dorfman disease represents a benign histiocytopathy of resident dendritic cell derivation.³ A characteristic immunohistochemical finding is S-100 positivity, which might suggest a Langerhans cell transdifferentiation phenotype, but other markers corroborative of a Langerhans cell phenotype—namely CD1a and langerin—will be negative. Biopsies typically show a mid to deep dermal histiocytic infiltration in a variably dense polymorphous inflammatory cell background comprised of a mixture of lymphocytes, plasma cells, and neutrophils.³ At times the extent of lymphocytic infiltration can be to a magnitude that resembles a lymphoma on histopathology. In our patient, lymphoma was excluded based on clinical presentation, as this patient lacked the typical symptoms of lymphadenopathy or B symptoms that come with B-cell lymphoma.⁵

The histiocytes in CRDD are characteristically large mononuclear cells exhibiting a low nuclear to cytoplasmic ratio reflective of the voluminous, nonvacuolated, watery cytoplasm. They have ill-defined cytoplasmic membranes resulting in a seemingly syncytial growth pattern. A hallmark of the histiocytes is emperipolesis characterized by intracytoplasmic localization of intact inflammatory cells including neutrophils, lymphocytes, and plasma cells.³

The differential diagnosis of CRDD includes Langerhans cell histiocytosis (LCH), indeterminate cell histiocytosis, xanthogranuloma, and reticulohistiocytoma. All of these conditions can be differentiated by their unique histopathologic and phenotypic characteristics.

Langerhans cell histiocytosis is a distinct clonal histiocytopathy that has a varied presentation ranging from cutaneous confined cases manifesting as a solitary lesion to one of disseminated cutaneous disease with the potential for multiorgan involvement. Regardless of the variant of LCH, the hallmark cell is one showing an eccentrically disposed, reniform nucleus with an open chromatin and abundant eosinophilic cytoplasm (Figure 1).⁶ Both LCH and CRDD stain positive for S-100. However, unlike the histiocytes in CRDD, those seen in LCH stain positive for CD1a and langerin and would not express factor XIIIA. Additionally, the neoplastic cells would not exhibit the same extent of CD68 positivity seen in CRDD.⁶ Treatment of LCH depends on the extent of disease, especially for the presence or absence of extracutaneous disease.⁷

A variant of LCH is indeterminate cell histiocytosis, which can be seen in neonates or adults. It represents a neoplastic proliferation of Langerhans cells that are devoid of Birbeck granules, reflective of an immature early phase of differentiation in the skin prior to the cells acquiring the Birbeck granule (as would be seen in neonates) or a later phase of differentiation after the mature Langerhans cell has encountered antigen and is en route to the lymph node (typically seen in adults).⁸ The phenotypic profile is identical to conventional LCH except the cells do not express langerin. Microscopically, the infiltrates are composed of Langerhans cells that are morphologically indistinguishable from classic LCH but without epidermotropism and exhibit a dominant localization in the dermis typically unassociated with other inflammatory cell elements (Figure 2).⁹

Xanthogranuloma is seen in young children (juvenile xanthogranuloma) as a solitary lesion, though a multifocal cutaneous variant and extracutaneous presentations have been described. Similar lesions can be seen in adults.¹⁰ These lesions are evolutionary in their morphology. In the inception of a juvenile xanthogranuloma, the lesions are highly cellular, and the histiocytes typically are poorly lipidized; there may be a dearth of other inflammatory cell elements. As the lesions mature, the histiocytes become lipidized, and characteristic Touton giant cells that exhibit a wreath of nuclei with peripheral lipidization may develop (Figure 3). In the later stages, there is considerable hyalinizing fibrosis, and the cells can acquire a spindled appearance. The absence of emperipolesis and the presence of notable lipidization are useful light microscopy features differentiating xanthogranuloma from CRDD.¹¹ Treatment of xanthogranuloma can range from a conservative monitoring approach to an aggressive approach combining various antineoplastic therapies with immunosuppressive agents.¹²

Solitary and multicentric reticulohistiocytoma is another form of resident dendritic cell histiocytopathy that can resemble Rosai-Dorfman disease. It is a dermal histiocytic infiltrate accompanied by a polymorphous inflammatory cell infiltrate (Figure 4) and can show variable fibrosis.¹³ One of the hallmarks is the distinct amphophilic cytoplasms, possibly attributable to nuclear DNA released into the cytoplasm from effete nuclei.¹³ The solitary form is unassociated with systemic disease, whereas the multicentric variant can be a paraneoplastic syndrome in the setting of solid and hematologic malignancies.¹⁴ In addition, in the multicentric variant, similar lesions can affect any organ but there can be a proclivity to involve the hand and knee joints, leading to a crippling arthritis.¹⁵ We presented a case of CRDD, a benign resident dendritic cell histiocytopathy that can manifest as a cutaneous confined process in the skin where the clinical course is characteristically benign. It potentially can be confused with LCH, indeterminate cell histiocytosis, xanthogranuloma, and reticulohistiocytoma. For a solitary lesion, intralesional triamcinolone injection and excision are options. Multifocal cutaneous disease or CRDD with notable extracutaneous disease may require systemic treatment.16 In our patient, one intralesional triamcinolone injection was performed with notable resolution.

The Diagnosis: Cutaneous Rosai-Dorfman Disease

Rosai-Dorfman disease is a rare benign non- Langerhans cell histiocytopathy that can manifest initially with lymph node involvement—classically, massive painless cervical lymphadenopathy.¹ Cutaneous Rosai-Dorfman disease (CRDD) is a variant that can be associated with lymph node and internal involvement, but more than 80% of cases lack extracutaneous involvement.^2,3 In cases with extracutaneous involvement, lymph node disease is most frequent.3 Cutaneous Rosai-Dorfman disease unassociated with extracutaneous disease is a benign self-limiting histiocytopathy that manifests as painless red-brown, yellow, or fleshcolored nodules, plaques, or papules that may become tender or ulcerated.⁴

Cutaneous Rosai-Dorfman disease represents a benign histiocytopathy of resident dendritic cell derivation.³ A characteristic immunohistochemical finding is S-100 positivity, which might suggest a Langerhans cell transdifferentiation phenotype, but other markers corroborative of a Langerhans cell phenotype—namely CD1a and langerin—will be negative. Biopsies typically show a mid to deep dermal histiocytic infiltration in a variably dense polymorphous inflammatory cell background comprised of a mixture of lymphocytes, plasma cells, and neutrophils.³ At times the extent of lymphocytic infiltration can be to a magnitude that resembles a lymphoma on histopathology. In our patient, lymphoma was excluded based on clinical presentation, as this patient lacked the typical symptoms of lymphadenopathy or B symptoms that come with B-cell lymphoma.⁵

The histiocytes in CRDD are characteristically large mononuclear cells exhibiting a low nuclear to cytoplasmic ratio reflective of the voluminous, nonvacuolated, watery cytoplasm. They have ill-defined cytoplasmic membranes resulting in a seemingly syncytial growth pattern. A hallmark of the histiocytes is emperipolesis characterized by intracytoplasmic localization of intact inflammatory cells including neutrophils, lymphocytes, and plasma cells.³

The differential diagnosis of CRDD includes Langerhans cell histiocytosis (LCH), indeterminate cell histiocytosis, xanthogranuloma, and reticulohistiocytoma. All of these conditions can be differentiated by their unique histopathologic and phenotypic characteristics.

Langerhans cell histiocytosis is a distinct clonal histiocytopathy that has a varied presentation ranging from cutaneous confined cases manifesting as a solitary lesion to one of disseminated cutaneous disease with the potential for multiorgan involvement. Regardless of the variant of LCH, the hallmark cell is one showing an eccentrically disposed, reniform nucleus with an open chromatin and abundant eosinophilic cytoplasm (Figure 1).⁶ Both LCH and CRDD stain positive for S-100. However, unlike the histiocytes in CRDD, those seen in LCH stain positive for CD1a and langerin and would not express factor XIIIA. Additionally, the neoplastic cells would not exhibit the same extent of CD68 positivity seen in CRDD.⁶ Treatment of LCH depends on the extent of disease, especially for the presence or absence of extracutaneous disease.⁷

A variant of LCH is indeterminate cell histiocytosis, which can be seen in neonates or adults. It represents a neoplastic proliferation of Langerhans cells that are devoid of Birbeck granules, reflective of an immature early phase of differentiation in the skin prior to the cells acquiring the Birbeck granule (as would be seen in neonates) or a later phase of differentiation after the mature Langerhans cell has encountered antigen and is en route to the lymph node (typically seen in adults).⁸ The phenotypic profile is identical to conventional LCH except the cells do not express langerin. Microscopically, the infiltrates are composed of Langerhans cells that are morphologically indistinguishable from classic LCH but without epidermotropism and exhibit a dominant localization in the dermis typically unassociated with other inflammatory cell elements (Figure 2).⁹

Xanthogranuloma is seen in young children (juvenile xanthogranuloma) as a solitary lesion, though a multifocal cutaneous variant and extracutaneous presentations have been described. Similar lesions can be seen in adults.¹⁰ These lesions are evolutionary in their morphology. In the inception of a juvenile xanthogranuloma, the lesions are highly cellular, and the histiocytes typically are poorly lipidized; there may be a dearth of other inflammatory cell elements. As the lesions mature, the histiocytes become lipidized, and characteristic Touton giant cells that exhibit a wreath of nuclei with peripheral lipidization may develop (Figure 3). In the later stages, there is considerable hyalinizing fibrosis, and the cells can acquire a spindled appearance. The absence of emperipolesis and the presence of notable lipidization are useful light microscopy features differentiating xanthogranuloma from CRDD.¹¹ Treatment of xanthogranuloma can range from a conservative monitoring approach to an aggressive approach combining various antineoplastic therapies with immunosuppressive agents.¹²

Solitary and multicentric reticulohistiocytoma is another form of resident dendritic cell histiocytopathy that can resemble Rosai-Dorfman disease. It is a dermal histiocytic infiltrate accompanied by a polymorphous inflammatory cell infiltrate (Figure 4) and can show variable fibrosis.¹³ One of the hallmarks is the distinct amphophilic cytoplasms, possibly attributable to nuclear DNA released into the cytoplasm from effete nuclei.¹³ The solitary form is unassociated with systemic disease, whereas the multicentric variant can be a paraneoplastic syndrome in the setting of solid and hematologic malignancies.¹⁴ In addition, in the multicentric variant, similar lesions can affect any organ but there can be a proclivity to involve the hand and knee joints, leading to a crippling arthritis.¹⁵ We presented a case of CRDD, a benign resident dendritic cell histiocytopathy that can manifest as a cutaneous confined process in the skin where the clinical course is characteristically benign. It potentially can be confused with LCH, indeterminate cell histiocytosis, xanthogranuloma, and reticulohistiocytoma. For a solitary lesion, intralesional triamcinolone injection and excision are options. Multifocal cutaneous disease or CRDD with notable extracutaneous disease may require systemic treatment.16 In our patient, one intralesional triamcinolone injection was performed with notable resolution.

The Diagnosis: Cutaneous Rosai-Dorfman Disease

Rosai-Dorfman disease is a rare benign non- Langerhans cell histiocytopathy that can manifest initially with lymph node involvement—classically, massive painless cervical lymphadenopathy.¹ Cutaneous Rosai-Dorfman disease (CRDD) is a variant that can be associated with lymph node and internal involvement, but more than 80% of cases lack extracutaneous involvement.^2,3 In cases with extracutaneous involvement, lymph node disease is most frequent.3 Cutaneous Rosai-Dorfman disease unassociated with extracutaneous disease is a benign self-limiting histiocytopathy that manifests as painless red-brown, yellow, or fleshcolored nodules, plaques, or papules that may become tender or ulcerated.⁴

Cutaneous Rosai-Dorfman disease represents a benign histiocytopathy of resident dendritic cell derivation.³ A characteristic immunohistochemical finding is S-100 positivity, which might suggest a Langerhans cell transdifferentiation phenotype, but other markers corroborative of a Langerhans cell phenotype—namely CD1a and langerin—will be negative. Biopsies typically show a mid to deep dermal histiocytic infiltration in a variably dense polymorphous inflammatory cell background comprised of a mixture of lymphocytes, plasma cells, and neutrophils.³ At times the extent of lymphocytic infiltration can be to a magnitude that resembles a lymphoma on histopathology. In our patient, lymphoma was excluded based on clinical presentation, as this patient lacked the typical symptoms of lymphadenopathy or B symptoms that come with B-cell lymphoma.⁵

The histiocytes in CRDD are characteristically large mononuclear cells exhibiting a low nuclear to cytoplasmic ratio reflective of the voluminous, nonvacuolated, watery cytoplasm. They have ill-defined cytoplasmic membranes resulting in a seemingly syncytial growth pattern. A hallmark of the histiocytes is emperipolesis characterized by intracytoplasmic localization of intact inflammatory cells including neutrophils, lymphocytes, and plasma cells.³

The differential diagnosis of CRDD includes Langerhans cell histiocytosis (LCH), indeterminate cell histiocytosis, xanthogranuloma, and reticulohistiocytoma. All of these conditions can be differentiated by their unique histopathologic and phenotypic characteristics.

Langerhans cell histiocytosis is a distinct clonal histiocytopathy that has a varied presentation ranging from cutaneous confined cases manifesting as a solitary lesion to one of disseminated cutaneous disease with the potential for multiorgan involvement. Regardless of the variant of LCH, the hallmark cell is one showing an eccentrically disposed, reniform nucleus with an open chromatin and abundant eosinophilic cytoplasm (Figure 1).⁶ Both LCH and CRDD stain positive for S-100. However, unlike the histiocytes in CRDD, those seen in LCH stain positive for CD1a and langerin and would not express factor XIIIA. Additionally, the neoplastic cells would not exhibit the same extent of CD68 positivity seen in CRDD.⁶ Treatment of LCH depends on the extent of disease, especially for the presence or absence of extracutaneous disease.⁷

A variant of LCH is indeterminate cell histiocytosis, which can be seen in neonates or adults. It represents a neoplastic proliferation of Langerhans cells that are devoid of Birbeck granules, reflective of an immature early phase of differentiation in the skin prior to the cells acquiring the Birbeck granule (as would be seen in neonates) or a later phase of differentiation after the mature Langerhans cell has encountered antigen and is en route to the lymph node (typically seen in adults).⁸ The phenotypic profile is identical to conventional LCH except the cells do not express langerin. Microscopically, the infiltrates are composed of Langerhans cells that are morphologically indistinguishable from classic LCH but without epidermotropism and exhibit a dominant localization in the dermis typically unassociated with other inflammatory cell elements (Figure 2).⁹

Xanthogranuloma is seen in young children (juvenile xanthogranuloma) as a solitary lesion, though a multifocal cutaneous variant and extracutaneous presentations have been described. Similar lesions can be seen in adults.¹⁰ These lesions are evolutionary in their morphology. In the inception of a juvenile xanthogranuloma, the lesions are highly cellular, and the histiocytes typically are poorly lipidized; there may be a dearth of other inflammatory cell elements. As the lesions mature, the histiocytes become lipidized, and characteristic Touton giant cells that exhibit a wreath of nuclei with peripheral lipidization may develop (Figure 3). In the later stages, there is considerable hyalinizing fibrosis, and the cells can acquire a spindled appearance. The absence of emperipolesis and the presence of notable lipidization are useful light microscopy features differentiating xanthogranuloma from CRDD.¹¹ Treatment of xanthogranuloma can range from a conservative monitoring approach to an aggressive approach combining various antineoplastic therapies with immunosuppressive agents.¹²

Solitary and multicentric reticulohistiocytoma is another form of resident dendritic cell histiocytopathy that can resemble Rosai-Dorfman disease. It is a dermal histiocytic infiltrate accompanied by a polymorphous inflammatory cell infiltrate (Figure 4) and can show variable fibrosis.¹³ One of the hallmarks is the distinct amphophilic cytoplasms, possibly attributable to nuclear DNA released into the cytoplasm from effete nuclei.¹³ The solitary form is unassociated with systemic disease, whereas the multicentric variant can be a paraneoplastic syndrome in the setting of solid and hematologic malignancies.¹⁴ In addition, in the multicentric variant, similar lesions can affect any organ but there can be a proclivity to involve the hand and knee joints, leading to a crippling arthritis.¹⁵ We presented a case of CRDD, a benign resident dendritic cell histiocytopathy that can manifest as a cutaneous confined process in the skin where the clinical course is characteristically benign. It potentially can be confused with LCH, indeterminate cell histiocytosis, xanthogranuloma, and reticulohistiocytoma. For a solitary lesion, intralesional triamcinolone injection and excision are options. Multifocal cutaneous disease or CRDD with notable extracutaneous disease may require systemic treatment.16 In our patient, one intralesional triamcinolone injection was performed with notable resolution.