Epithelial-myoepithelial carcinoma of parotid gland: a case report with immunohistochemical and ultrastructural studies

A 66-year-old man presented with a painless mass of the parotid gland. Light and electron microscopic studies verified the basic nature of the tumor as epithelial-myoepithelial carcinoma, a low-grade malignant neoplasm of the salivary gland. Pathologically, there were two types of cells; the inner eosinophilic epithelial cells lining the ducts and the outer clear cells. The former cells displayed immunoreactivity for cytokeratin and ultrastructural features of apical microvilli and desmosome. The latter cells were positive for actin, S-100 protein, vimentin and the cytoplasm contained actin microfilaments. Such pathological findings were characteristic features of this rare tumor. To our knowledge, this is the first reported case of EMC in Thailand.