Oncocytoma of the parotid gland: Neoplasm or nodular hyperplasia?

In a histologic re-examination and re-classification of parotid tumors in 1,678 patients treated by surgery, 13 cases of oncocytoma were found. Five patients had bilateral tumors. The cell picture in oncocytoma is very characteristic, made up of oncocyte-like cells with eosinophilically granulated abundant cytoplasm, and often also of clear cells. Metastases or death in oncocytoma did not occur in any case, but local “recurrence” was seen in 4 of the 13 cases. Oncocytoma often shows multinodular growth, and oncocytic foci are very often found in the surrounding glandular tissue. Of the 5 patients who had bilateral tumors, 2 had synchronous tumors. The high frequency of multinodular and bilateral growth observed in the present series supports earlier theories that oncocytoma is not a real neoplasm but a nodular hyperplasia. The main differential diagnoses are benign mixed tumor with oncocytic foci and acinic cell carcinoma.