Ultrastructurally abnormal mitochondria in the pituitary oncocytoma.

A pituitary adenoma in a 67-year-old man was characterized by abundant mitochondria and identified as an oncocytoma, which clinically and histologically appeared as a chromophobe adenoma. In addition to the numerous mitochondria within the neoplastic cells, structurally abnormal mitochondria were also present. Compared with other pituitary oncocytomas reported in the literature, abnormally structured mitochondria appear rare among the mitochondrial population of pituitary oncocytomas.