Benign and Malignant Oncocytoma of the Salivary Glands with an Immunohistochemical Evaluation of Ki-67

We present two cases of benign oncocytoma derived from the parotid gland and minor salivary gland and one case of malignant oncocytoma from the parotid gland. The proliferative activity of the tumor cells was evaluated immunohistochemically for Ki-67. The average frequency of Ki-67-positive cells was 3.3% in the benign oncocytomas and 6.5% in the malignant oncocytoma. The higher frequency of Ki-67-positive cells in the malignant oncocytoma might reflect active cell proliferation. Ki-67 immunostaining may be useful in distinguishing a benign oncocytoma from a malignant oncocytoma.