Oncocytoid adenocarcinoma of the parotid gland. Cytologic, histologic and ultrastructural findings.

An oncocytoid adenocarcinoma of the parotid gland, diagnosed by fine needle aspiration cytology, is reported. The neoplasm, seen in a 66-year-old man, metastasized to 33 of 46 resected cervical lymph nodes; the patient is currently free of disease 17 months after surgery. Cytologically, the neoplastic cells occurred singly and in small clusters. They had abundant granular cytoplasm with occasional vacuoles, large nuclei and prominent nucleoli. Ultrastructurally, the tumor cells had copious cytoplasm, with moderately increased numbers of mitochondria, dilated endoplasmic reticulum, mucin droplets and intracytoplasmic lumina. The clinical importance of distinguishing this neoplasm from true malignant oncocytoma is, at present, unknown.