Background: Myoepitheliomas are tumors composed predominantly or exclusively of myoepithelial cells, usually arising in salivary glands. Cutaneous/soft tissue localization is very rare, especially for the malignant myoepitheliomas.
Case report: We presented a case of myoepithelial carcinoma involving subcutaneous adipose tissue of the left forearm in a woman aged 62 years. The tumor was composed of epithelioid and hyaline cell types, arranged in diffuse sheets, nests and loose clusters within hyalinized and myxoid matrix. The neoplasm displayed high-grade cytologic atypia with some cells having pleomorphic, hyperchromatic nuclei, and others showing vesicular nuclei, large nucleoli with scattered bizarre giant cells. High mean mitotic count of 7 mitoses/10 high power filds and extensive necrosis favoured the diagnosis of malignancy. Immunohistochemical staining was positive for cytokeratin (AE1/AE3), epithelial membrane antigen, S-100 protein, glial fibrillary acidic protein, and vimentin.
Conclusion: Considering the subcutaneous localization, myoepithelial immunophenotype and high-grade cytologic atypia the neoplasm was classified as a soft-tissue myoepithelial carcinoma.