Malignant oncocytoma of the parotid gland.

A 57-year-old woman was first seen in the ENT clinic of Osaka University Hospital with a complaint of recent enlargement of a painless mass at the right parotid region of 35 years' duration. A smooth surfaced, elastic mass of about 5 × 6cm was palpated at the right subauricular area extending to the submandibular region. The mass was not adhered to the skin. There was no other otolaryngologic, hematologic or urinary abnormality defected, and no cervical lymph node was palpable, and the facial nerve function was normal. Sialography showed a suspicion of obstruction of the duct due to malignancy. CT scanning revealed a partially irregular, round mass at the right parotid region. Subtotal parotidectomy under general anesthesia was performed, and the well-capsulated tumor mostly located in the superficial lobe of the parotid gland and partially advanced to the deep lobe to surround the facial nerve was removed. Light-and electron-microscopic examination revealed malignant oncocytoma characterized by the marked enlargement of eosinophilic cytoplasma.