Recurrent oncocytoma of the ethmoid sinus with orbital invasion.

A patient is presented with recurrent oncocytic tumor that arose from the lateral nasal wall and posterior ethmoid sinus and then invaded the orbit. The diagnosis of an oncocytic lesion was made from the masses of intracellular mitochondria noted on electron microscopy. The malignant character of the tumor was evident from its local aggressiveness. In agreement with earlier authors, we believe that oncocytic tumors of the nose and paranasal sinuses should be classified as low-grade malignancies.