Clear cell myoepithelial carcinoma of the skin. A case report.

Myoepitheliomas are tumors of myoepithelial cells, most frequently diagnosed in the salivary glands. Cutaneous location is very rare, especially for malignant variant. We report a case of recurrent cutaneous myoepithelial carcinoma of the femoral region in a 51-year-old woman. Histologically, the tumor was confined to the dermis and superficial subcutaneous fat tissue, exhibiting typical multinodular pattern. The majority of tumor cells were of clear cell type, although rare epithelioid and spindle cells were also present. Nuclear atypia, mitotic activity of 12 mitoses per 10 microscopic high power fields and Ki-67 labeling index of 20%, as well as three recurrences, corroborated the malignant nature of the tumor. Immunohistochemistry showed positivity for cytokeratin, epithelial membrane antigen, vimentin, S-100 protein and myogenic markers (alpha-smooth muscle actin and muscle-specific actin HHF-35) in keeping with the myoepithelial cell immunophenotype. Staining for CD34, desmin and HMB-45 was negative. Myoepithelial carcinoma should be considered in the differential diagnosis of cutaneous neoplasms composed predominantly of clear cells.