Oncocytoma of the Parotid Gland and its Mimickers: A Comprehensive Review

Oncocytomas are benign neoplasms composed of oncocytes; the large eosinophilic      cuboidal to columnar cells with more than 60% of their cytoplasm occupied by mitochondria. Oncocytomas represent less than 1% of the salivary gland neoplasms and 82% to 90% of them occur in the parotid gland. Salivary gland oncocytomas constitute 2.5% of the parotid gland tumors. Despite the well-recognized morphology of this tumor, there is a wide range of neoplasms that may mimic oncocytoma and hence need to be considered in its differential diagnosis. A predominantly clear cell variant of oncocytoma may resemble a number of salivary gland neoplasms where clear  cells   may   be  prominent.   In  addition,  oncocytic  metaplasia may be a focal or an extensive component of other distinct salivary gland neoplasms. An awareness of all the possible “mimickers” of clear cell oncocytoma becomes more significant in view of the fact that most are malignant neoplasms with a poor prognosis.