Diagnosis: Eruptive keratoacanthomas
Keratoacanthomas (KAs) most commonly affect people between the ages of 50 and 69 years old, although there have been reports in all age groups, including children. Studies have additionally revealed an equal distribution in prevalence between the sexes.
KAs are common, frequently self-limiting, epidermal tumors that consist of keratinizing squamous cells, thought to arise from the seboglandular part of the hair follicle. KAs have been divided into two general categories consisting of solitary and multiple types. Although the solitary type is most commonly observed, the multiple KAs category may be further subdivided to include the Ferguson-Smith type, which involves multiple self-healing KAs, generalized eruptive KA, which involves both skin and mucosa, multiple familial KA, multiple KA in association with Muir-Torre syndrome, and multiple KA centrifugum marginatum.
There are numerous factors implicated in the development of KAs, including trauma, light, exogenous carcinogens, impaired cell-mediated immunity, and immunosuppressive medications. A KA, which may be asymptomatic, slightly tender, or pruritic, initially forms as a small red macule and then evolves into a rapidly-growing (2 to 8 weeks) firm papule with scale. The papule then becomes a round, firm and raised skin-colored to pink nodule with a central keratin plug at the peak.
Histopathology varies depending upon the developmental stage of the lesion when biopsied. KA formation is comprised of 3 stages that may be recognized clinically and histologically, including the early-growing phase, the fully developed (stationary) phase and the senescent phase. Although not unique to KAs, histology may commonly show reactive proliferation of eccrine gland ducts beneath the tumor lobules. The ducts may adopt an adenomatoid appearance, as they lose their two-layer cellular construct.
The controversy regarding KA’s benign or malignant nature remains. Therefore, diagnosis is frequently confirmed through biopsy, in order to rule out squamous cell carcinoma. Although most KAs may resolve spontaneously, patients who find the lesions cosmetically unacceptable or painful may seek treatment. Nonsurgical modalities should be utilized before surgery, as surgical removal may leave scarring. Nonsurgical treatment options include local and systemic therapies, as well as electrodessication and curettage and laser therapy. A promising agent emerging in the treatment of KAs is 5-fluorouracil, which may be used as an intralesional injection, topically, or combined with lasers, leading to optimal cosmetic results with rapid clearance. The patient and family reported a noticeable improvement in appearance two weeks after discontinuing the new therapy.
Dr. Bilu Martin is in private practice at Premier Dermatology, MD, in Aventura, Fla. More diagnostic cases are available at edermatologynews.com. To submit your case for possible publication, send an email to [email protected].