Cutaneous Myoepithelial Carcinoma Arising Within Syringocystadenoma Papilliferum.

Benign and malignant tumors derived from myoepithelial cells represent a rare group of tumors that may arise from salivary gland as well as breast, lung, and more rarely, skin. Cutaneous lesions showing myoepithelial origin include benign mixed tumor of skin (chondroid syringoma) in addition to much less common tumors composed entirely of myoepithelial cells, including benign myoepithelioma and malignant myoepithelial carcinoma. Variability in morphologic and phenotypic findings may result in a diagnostic challenge, especially in pure myoepithelial neoplasms. While some myoepithelial neoplasms may demonstrate overtly benign or malignant features, there are also reports of metastases arising from tumors lacking malignant histopathologic features, further challenging classification and prognostication of this group of tumors. Myoepithelial tumors arising within adnexal and salivary gland neoplasms have been reported. We report a unique case of myoepithelial carcinoma arising in association with a precursor syringocystadenoma papilliferum.