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Case Reports

Abstract

Myoepithelial carcinomas arise most frequently from myoepithelial cells within the salivary glands with primary cutaneous tumors less frequently encountered. Herein we describe a primary cutaneous desmoplastic myoepithelial carcinoma arising in an 89-year-old male. The patient presented with a slowly enlarging, pink, telangiectatic plaque on the parietal scalp.   

Histopathology showed a plaque-like adnexal tumor that displayed myxoid, sclerotic, and fibrotic zonation. A highly infiltrative epithelial component exhibited cordlike, nested, and lobular morphology with focal ductal differentiation.  Via immunohistochemistry, there was co-expression of SOX10 and p40, EMA  positivity, and a lack of INSM-1 expression. MelanA, CEA, and Ber-EP4 immunohistochemical stains were negative. While desmoplastic adenoid cystic carcinoma and desmoplastic cylindrocarcinoma were considered, the histologic and immunophenotypic features were favored to represent desmoplastic myoepithelial carcinoma.  

The lesion was surgically excised with wide margins. Follow-up 7 months later revealed no evidence of local recurrence or distant metastasis. Accurate diagnosis of cutaneous myoepithelial carcinoma is essential due to its metastatic potential and overlap with other adnexal tumors. The diagnostic process relies on histopathological evaluation, noting the multiphasic or heterogeneous cell populations, growth patterns, and immunohistochemical profile (positivity for SOX10 or S100, cytokeratins and/or EMA, and p40 or p63). Molecular studies can aid in distinguishing it from mimics, and the mainstay of treatment remains wide local excision.