Incidental adenomas of the human pituitary gland.

Using conventional histological technique, we investigated 44 adenomas (31 men, 13 women) incidentally found in 36 pituitaries (25 men, 11 women) obtained from 1,117 unselected autopsies. The overall incidence of adenomas was 3.2% (men, 3.8%; women, 2.4%) without any significant sex predominance. Size, age distribution, and histological appearances of these adenomas were similar to those previously reported by others. Statistical analysis showed that the adenomas had a predilection for occurrence at the anterior margin of the gland. We further investigated 33 available adenomas with immunohistochemistry using antibodies for various adenohypophyseal hormones, S-100 protein, and glial fibrillary acidic protein, of which 6 contained growth hormone, 3 contained growth hormone and prolactin, 7 contained prolactin, 6 contained follicle-stimulating hormone, 3 contained follicle-stimulating and luteinizing hormones, 2 contained thyroid-stimulating and adrenocorticotrophic hormones (separately), and 6 contained no adenohypophyseal hormones. None of adenomas revealed neoplastic proliferation of folliculostellate cells. To investigate tumor proliferation, nucleolar organizer regions were studied in 9 adenomas using the argyrophil method. The mean number per nucleus was slightly higher than that of corresponding, nontumorous adenohypophysis at a statistically significant level. No adenoma caused symptoms of adenohypophyseal hormone abnormalities.