Myoepithelioma of the soft palate: Report of an unusual case and review of the literature

Salivary gland myoepithelioma (myoepithelial adenoma) is a rare tumor derived from myoepithelial cells. It represents less than 1% of all salivary gland tumors and presents several growth patterns. The parotid and palate are the sites of predilection. In this paper we present an unusual case of myoepithelioma of the soft palate in a 51-year-old woman. The tumor was well circumscribed, with an initial differential diagnosis between pleomorphic adenoma and adenocystic carcinoma. The histopathologic findings showed 2 types of cells, while the immunohistochemical profile revealed a positive reactivity of specified cells to S-100 protein, to the smooth muscle actin (SMA) and to the cytokeratin. All these findings indicated a case of myoepithelioma that focally revealed areas of atypia and necrosis. This appearance is extremely rare and could lead to the diagnosis of malignant transformation of a myoepithelioma of the salivary glands or a myoepithelial carcinoma. Histology, immunohistochemistry, and differential diagnosis of this rare neoplasm is discussed. Also, a brief review of myoepitheliomas and their malignant counterparts is presented.