Cutaneous myoepithelial tumors are rare neoplasms but are being increasingly recognized and reported in the literature.1-7 Myoepithelial tumors are related to benign mixed tumors of the skin but lack the epithelial ductules that are present in mixed tumors. Cutaneous myoepithelial tumors may show a variety of architectural, cytological, and stromal features. Their immunophenotype usually is characterized by coexpression of an epithelial marker (eg, keratin, epithelial membrane antigen [EMA]) and S-100 protein; they also may express a variety of other myoepithelial markers, including keratins, smooth muscle actin, calponin, glial fibrillary acidic protein, p63, and desmin.7 EWS RNA binding protein 1 (EWSR1) and pleomorphic adenoma gene 1 (PLAG1) gene rearrangement has been detected in subsets of these tumors on in situ hybridization.8-10
Malignant myoepithelial tumors of the skin, also referred to as cutaneous myoepithelial carcinomas, are exceedingly rare. Including the current case, a search of PubMed articles indexed for MEDLINE and Google Scholar using the terms myoepithelial carcinoma and cutaneous revealed 12 cases that have been reported in the literature (Table).1-7,11-13 These tumors often occur in the head and neck areas and the lower extremities and display a bimodal age distribution, generally occurring in patients younger than 21 years and older than 50 years of age; they also show a slight female predominance. Available follow-up data from the literature have shown local recurrence or metastasis in 3 cases3,4,6; however, in one case the metastatic focus was not histologically identified.4 Cutaneous myoepithelial carcinoma presenting with metastatic disease further limits treatment options. Here, we describe a case of metastatic cutaneous myoepithelial carcinoma in a 47-year-old man, a rare example of cutaneous myoepithelial carcinoma with histologically documented metastatic disease at the initial presentation.
A 47-year-old man who underwent a renal transplant 19 years prior presented with a weeping, ulcerated, mildly tender lesion on the scalp of 4 months’ duration with neck and back pain of 3 months’ duration. Physical examination demonstrated a 6-cm area of ulceration on the anterior crown of the scalp with adjacent enlarged keratoacanthomalike craters and satellite nodules (Figure 1). He was previously diagnosed with basal cell carcinoma (BCC) of the scalp at an outside institution 4 years prior and was treated with radiation therapy. The prior scalp biopsy for BCC diagnosis was unavailable for review. The patient had a history of chronic eczematous dermatitis in the waistband area that had been present for 19 years and another BCC with nodular and infiltrative patterns on the left helix. Of note, he also had been taking long-term immunosuppressant medications (ie, cyclosporine, azathioprine) for maintenance following the renal transplant.
Because of the extensive ulceration of the primary lesion, a shave biopsy of the scalp was performed on an adjacent satellite nodule. Histopathologic findings showed an intradermal neoplasm characterized by poorly cohesive cells exhibiting epithelioid to plasmacytoid morphologic features surrounded by abundant chondromyxoid stroma. Ductular differentiation was not identified (Figure 2A). The neoplastic cells displayed hyperchromatic nuclei with marked nuclear pleomorphism and atypical mitotic figures (Figure 2B). On immunohistochemistry the tumor cells stained positive for cytokeratin AE1/AE3 (Figure 3), S-100 protein (Figure 4), and p63, and were negative for calponin, desmin, melan-A, cytokeratin 7, and brachyury (Figure 5).
Radiographic imaging was performed due to the patient’s history of neck and back pain. Magnetic resonance imaging showed innumerable slightly expansile, T1-hypointense, T2-hyperintense, and robustly enhancing lesions involving the cervical, thoracic, lumbar, and sacral spine, as well as the thoracic ribs and bilateral iliac bones. There was no evidence of soft tissue tumor around the bone lesions. Ventral cervical spinal cord compression was detected at the C4 vertebra, causing a symptomatic radiculopathy; however, due to widely metastatic disease, the patient was not considered appropriate for neurosurgical intervention of the compression. Computerized tomography of the chest, abdomen, and pelvis did not identify any visceral source of malignancy, though multiple bilaterally enlarged cervical lymph nodes were identified on magnetic resonance imaging.
Fine needle aspiration of a left iliac bone lesion demonstrated neoplastic cells and chondromyxoid stroma essentially identical to the features shown in the skin biopsy (Figure 6). Given the morphologic features of the tumor and coexpression of cytokeratin and S-100 protein, the findings were interpreted as primary cutaneous myoepithelial carcinoma with disseminated metastatic lesions. The patient began treatment with carboplatin and paclitaxel chemotherapy. To combat the symptomatic bone pain and upper extremity radiculopathy, palliative radiation was administered to the cervical spine, lumbar spine, and right sacrum (30 Gy to each site in 10 fractions at 3 Gy per fraction). Despite the attempted chemotherapy and radiation, the patient continued to decline, and after 2 months, he elected to pursue palliative care. The patient died after 3 months in palliative care (5 months after the initial presentation).