We studied the clinical, light microscopic and ultrastructural features of 5 patients with oncocytomas identified by electron microscopy. Their major symptoms were visual impairment, headache, and impotence, which had developed from 7 months to 2
years
before surgery. All the patients were macroadenomas with suprasellar extension by CT scan. Hormonal secretiory capacities for GH, PRL, cortisol, TSH were decreased in 4 patients tested, three of them had decreased FSH and LH responses. One had
elevated
basal FSH level. Light microscopy revealed varying degrees of the acidophilic cytoplasm with granularity. Two showed multifocally positive immunocytochemistry for FSH and/or LH. Electron microscopy revelaled that small polyhedral cells had round
to
irregular, often euchromatic nuclei, and poorly developed RER and Golgi complexes, however, markedly hyperplastic mitochondria occupied more than 50% of the cytoplasmic area. The mitochodria varied in size, number, electron density, and
morpholggy
of
the inner compartment. The small, often haloed secretory granules were sparse and located chiefly under the plasmalemma.
In this study, we could indentify oncocytoma from 5 surgically resected nonfunctioning pituitary adenomas by electron microscopy and present them with a literature review. Further study will be needed t clarify the cytogenesis and the meaning of
oncocytic transformation. (J Kor Soc Endorcinol 7:16~23, 1992).
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