Malignant oncocytoma of major salivary glands. Report of a post-irradiation case.

The fourth case of malignant oncocytoma arising in the submandibular gland is here reported. This tumor arose in a 48-year-old man after radiation exposure, a finding never described before for malignant oncocytoma. In addition, several regional metastatic lymph nodes were found. The diagnosis was confirmed by histochemical and ultrastructural findings. The tumor cells showed easily recognizable mucus production and, ultrastructurally, abundant mitochondria, intracytoplasmic lumina lined by microvilli and lipid droplets. These last features have only seldom been described in malignant oncocytoma. Furthermore, the neoplastic cells were alpha-1-antitrypsin positive and S100, thyroglobulin, carcinoembryonic antigen, and smooth muscle actin negative. A thorough review of the literature is also presented.