Epithelial-myoepithelial carcinoma of the salivary glands: a review of literature.

Epithelial-myoepithelial carcinoma (EMC) of the salivary glands is a rare tumor first described by Donath et al in 1972 and recognized as a distinct pathologic entity in the 1991 WHO classification. The EMC comprises approximately 1% of all salivary gland tumors. The histological hallmark is a biphasic cell arrangement formed by an inner layer of duct-forming epithelial cells and an outer layer of myoepithelial cells. The epithelial-myoepithelial dualism is confirmed using immunohistochemical methods: the epithelial cells are immunoreactive for low molecular weight keratin; the myoepithelial cells are immunoreactive for S-100 protein, muscle specific actin and vimentin. Most reported follow-up information indicates that EMC is a low-grade malignant tumor; however, from the analysis of the various series it is demonstrated that tumors with a solid growing pattern, nuclear atypia, DNA aneuploidy and high proliferative activity, generally have a more aggressive behavior and a higher frequency of local recurrences and metastases.