Oncocytic mucoepidermoid carcinoma of the parotid gland: case report

Mucoepidermoid carcinoma is the most common malignant tumour of salivary glands. Oncocytic variant is rare and could be mistaken for benign entities like oncocytoma and Warthin tumour on cytology. We present a case of a 67-year-old female presented with left parotid gland mass, which was diagnosed as a benign oncocytoma on cytologic examination. Later, the patient underwent left parotidectomy where the histologic examination revealed a malignant oncocytic mucoepidermoid carcinoma. The distinction between these entities is essential to get a proper management for the patient. On cytology alone, it is quite difficult to differentiate; however, histologic examination shows malignant features including infiltrative borders, lymphovascular invasion and perineural invasion excluding a benign tumour. The presence of mucin is an important clue to suspect oncocytic mucoepidermoid carcinoma. Ancillary studies can help reach a wright diagnose, as oncocytic mucoepidermoid carcinoma is positive for P63 and has MAML2 translocation.