Malignant oncocytoma of the parotid with oncocytic change of the contralateral gland

Abstract

(Editor’s Comment: The observations of oncocytic change in the contralateral gland raises the possibility of progression to malignancy.) The oncocytoma is a rare but well-known tumor of salivary gland origin, and it is generally regarded as benign. Various synonyms have been applied to this neoplasm (ie, oxyphilic adenoma, oxyphilic granular-cell adenoma, and oncocytic adenoma).l The hallmark of oncocytomas is the presence of true oncocytes. These true oncocytes are large epithelial cells with a distinctly eosinophilic, finely granular cytoplasm and a rounded vesicular nucleus that is usually centrally placed. These cells contain numerous mitochondria and enzymes on electronmicroscopic and histochemical studies.2*3 Oncocytes are commonly present in the parotid salivary gland, but they have been observed in other major and minor salivary glands; in the mucous glands of the larynx, trachea, bronchi, and esophagus; in the lacrimal glands; in the nasal mucous membrane; in the thyroid, parathyroid, and pancreas; in both lobes of the hypophysis; in testicle and fallopian tubes; in the liver; and in the stomach.4 Neoplastic oncocytomas arise in the parotid gland, the submaxillary gland, and the minor salivary glands. Their incidence varies from 0.5% to 1.2% of all parotid gland tumors.5-7 They are nearly always found in persons over 50 years old and in increasing numbers they are found in persons from 50 to 70 years old.*