Oncocytic mucoepidermoid carcinoma of the salivary glands.

Two parotid mucoepidermoid carcinomas with predominant oncocytic features were initially assessed on frozen section. Because of extensive oncocytic change, it was inferred that the lesions were most likely benign. Permanent sections revealed low-grade mucoepidermoid carcinoma with prominent oncocytic change (in more than 75% of the neoplasms) in both cases. Review of 48 additional consecutive cases of mucoepidermoid carcinoma of the salivary glands revealed prominent oncocytic change (accounting for 60% of the neoplasm) in one high-grade lesion. Phosphotungstic acid-hematoxylin stains revealed strong granular cytoplasmic staining in the oncocytic elements; immunohistochemical stains for antimitochondrial antibodies also showed intense immunoreactivity in these cells. Oncocytic change is not typically a prominent feature of mucoepidermoid carcinoma of the salivary glands, and to our knowledge, only three such cases have been reported previously. Because most salivary gland lesions with oncocytic change are benign, it is important to distinguish mucoepidermoid carcinoma from other entities that may show prominent oncocytic change. We report three additional examples of this rare lesion, two low-grade tumors and one high-grade tumor, and review our experience with oncocytic change in mucoepidermoid carcinoma of the salivary glands.