[Epithelial-myoepithelial carcinoma of the salivary glands. Study of 15 cases and review of the literature].

Epithelial-myoepithelial carcinoma initially described by Donath in 1972 represents about 0.5% of salivary gland tumors. Total number of reported cases brings to at least 56 cases; we add 15 personal cases. These 71 cases included 46 women and 25 men. The ages range from 23 to 91 years with peak incidence from the 6th to the 8th decades. The majority of tumors (58) arose in the parotid gland. Of the 71 patients local recurrences occurred in 20, cervical lymph node metastasis in 6 and 2 patients died of their disease. Epithelial-myoepithelial carcinoma typically have a multinodular growth pattern with islands of tumors separated by dense fibrous connective tissue. These tumor masses were composed of well-defined tubules lined by two layers of cells: outer cells are large clear with variable amount of glycogen, inner cells are small, cuboidal and eosinophilic. Perineural invasion and necrosis were occasionally seen. In some cases, this biphasic pattern was less apparent with solid masses of clear cells. Electron microscopic and immunohistochemical studies confirmed the epithelial and myoepithelial differentiation. The differential diagnosis included all clear cells tumors of salivary glands (mucoepidermoid carcinoma, acinic cell carcinoma, sebaceous carcinoma) and also metastatic renal carcinoma. Epithelial-myoepithelial carcinoma is a tumor of low-grade malignancy of duct origin which should be differentiated from salivary duct carcinoma.