Oncocytic Variant of Mucoepidermoid Carcinoma of Parotid Gland-Report of a case-

초록

Oncocytic variant of mucoepidermoid carcinoma of the salivary gland is rare. We present a case of oncocytic variant of mucoepidermoid carcinoma in the parotid gland. A 50-year-old male presented with a coin-sized, nonpainful, and slowly growing mass in the region of the right parotid gland, which had been present for a couple of years. On physical examination, there was a well demarcated nodular mass in the right parotid gland. Fine needle aspiration produced hypocelluar aspirate showing singles and clusters of some what bland-looking oncocytic epithelial cells suggesting benign oncocytic lesion. Superficial parotidectomy was performed. Gross examination revealed a well circumscribed but not encapsulated rubbery mass with pale tan cut surface, measuring 2×1.9×1.5㎝. Intraoperative frozen section demonstrated an infiltrative neoplasm, and was diagnosed as low mucoepidermoid carcinoma. Routinely processed histologic sections showed an infiltrative tumor, which were composed mainly of sheets of oncocytic epidermoid cells (more than 90% of tumor cells) characterized by bland and cuboidal to polygonal with small oval to round nuclei and small, prominent, central nucleoli. Minor foci of variable sized cysts lined by oncocytes and partly by mucus cells were evident. Mitotic figures and necrosis were not identified. There was no evidence of perineural invasion or vascular invasion. The tumor cells were positive for cytokeratin. Ki-67 labeling index was less than 1%. Recognition of this variant is important because oncocytic lesions of the parotid gland are usually benign and oncocytic change is not typically a prominent feature of mucoepidermoid carcinoma of the salivary gland.