Oncocytic mucoepidermoid carcinoma of the parotid gland: report of a case with DNA ploidy analysis and review of the literature.

A 44-year-old female presented with a painful mass in the left parotid gland. Histologic examination revealed the characteristic picture of oncocytic mucoepidermoid carcinoma (OMEC) composed mainly of sheets of oncocytic cells with uniform nuclei and eosinophilic cytoplasm, focally smaller epidermoid cells surrounding poorly formed glandular spaces, and a few cystic structures lined by well-differentiated mucous cells with intracytoplasmic mucin. Immunohistochemical staining with antimitochondrial antibody showed granular cytoplasmic positivity in oncocytic cells. The resulting histogram for DNA ploidy analysis was of diploid type. OMEC of the parotid gland is a recently described rare neoplasm. Only six cases have been previously reported in the literature. For an accurate approach in the management of patients, OMEC should be considered in the differential diagnosis of oncocytic lesions of the parotid gland, most of which are benign.