MALIGNANT ONCOCYTOMA OF THE PARANASAL SINUS

A case of malignant oncocytoma developing in the paranasal sinus of a 37-year-old Japanese man with a habit of heavy smoking is described. The primary tumor was found in the right maxillary sinus with local invasion to the nose and right ethmoidal sinus ; it was composed of nests of large oncocytic cells, with finely granular and eosinophilic cytoplasm, nuclear pleomorphism and prominent nucleoli, surrounded by proliferation of spindle-shaped cells in some areas. Electron microscopically, the cytoplasm of oncocytic tumor cells was characterized by abundant mitochondria, and immunohistochemical investigation revealed positive binding for antibodies to S-100 protein and α₁-antitrypsin, but a negative reaction for both cytokeratin and vimentin. At autopsy, metastatic nodules of tumor in the lungs, liver and pancreas independently exhibited both oncocytic cell- and sarcomatous cell compartments. This phenomenon is rare, and to the authors' knowledge, this would be histologically an ususual report of malignant oncocytoma with sarcomatous metastatic nodules arising from the paranasal sinus to be described in the literature