Malignant myoepithelioma (or myoepithelial carcinoma) is an uncommon malignant tumor newly adopted as a separate entity in the revised WHO classification of salivary gland tumors (1991).
Two criteria must be satisfied for the diagnosis of malignant myoepithelioma: (1) its neoplastic cells must be myoepithelial in nature, and (2) the tumor must be clinically identified as malignant. Although these criteria seem obvious, it is often difficult to diagnose this tumor definitively. In general, a combination of morphologic, ultrastructural, and immunohistochemical investigations is required to demonstrate myoepithelial differentiation in this tumor, and cytologic features indicating infiltrative growth must be reviewed to assess malignant potential. Most malignant myoepitheliomas occur in the parotid gland, but metastases are uncommon. Of 36 reported cases, 10 originated in the minor salivary gland and, 7 had metastasized to distant sites. We describe two cases of malignant myoepithelioma in which clinical and histopathological findings suggest malignant transformation.
