Apocrine epithelial-myoepithelial carcinoma of the parotid gland with concurrent oncocytic change: a novel variant.

ABSTRACT

Epithelial-myoepithelial carcinoma (EMCa) is a rare, low-grade, malignant salivary gland tumor. Here, we report an unusual case of an EMCa with extensive apocrine and oncocytic changes. The tumor occurred in the left parotid gland of a 68-year-old male. Histologically, the tumor was characterized by a biphasic arrangement of luminal ductal cells and abluminal polygonal myoepithelial cells, with prominent apocrine differentiation in the luminal layer and dense eosinophilic cytoplasm in both components. Immunohistochemically, the ductal epithelial component was positive for cytokeratin 7, androgen receptor, gross cystic disease fluid protein 15, and human epidermal growth factor receptor 2, and both components were diffusely positive for anti-mitochondria antibody and phosphotungstic acid-hematoxylin. EMCa with apocrine differentiation or oncocytic change is an uncommon variant. To the best of our knowledge, this report describes the first case of these 2 variants coexisting in EMCa tumor cells to be reported in the English-language literature. Awareness of the histopathologic features of EMCa is necessary to avoid making an incorrect diagnosis.