Epithelial-myoepithelial carcinoma of the palate.

A case of epithelial-myoepithelial carcinoma (EMC) of the palate in a 72-year-old Japanese man is described. The patient had noticed swelling of the palate commencing about 20 years previously. Histologically, the tumor consisted of a proliferation of double-layered duct-like structures with two distinctive cell types. The inner layer was composed of eosinophilic epithelial cells, while the outer layer was composed of clear cells. Immunohistochemical analysis revealed that reaction products for total keratin were predominantly found in the cytoplasm of the inner epithelial cells, while those for S-100 protein and smooth muscle actin were observed only in the outer cells. Immunoreactive products for secretory component and lysozyme were found in some of the luminal contents and the inner cells of the tumor nests. These findings indicated this tumor to be an EMC of the palate, which had shown no aggressiveness over a twenty-year period prior to surgical excision. [ABSTRACT FROM AUTHOR]