Pituitary oncocytic tumor with Cushing's disease.

Pituitary adenomas composed of oncocytes are rare. We report a young female with an atypical oncocytic tumor of the pituitary. The histology was unusual because the oncocytic cells--in addition to an abundance of abnormal mitochondria--contained a conspicuous smooth endoplasmic reticulum. The tumor grew invasively and the patient developed adrenal hypercorticism.