Monomorphous plurihormonal adenoma of the human pituitary. A histologic, immunocytologic and ultrastructural study

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Abstract
A well-developed 23-yr-old man, complaining of blurred vision but with no endocrine symptoms, had a large pituitary adenoma spreading outside the sella. Endocrine investigations disclosed growth hormone deficiency, hyperprolactinemia (responsive to TRH), and very high blood .alpha.-subunit (72 ng/ml) level. Histology showed a chromophobic, slightly acidophilic pituitary adenoma with focal fibrosis and calcification. The immunoperoxidase technique revealed prolactin and .alpha.-subunit in the cytoplasm of a single-cell type, at the light and EM microscopic level, indicating that monomorphous, plurihormonal adenomas exist in the human pituitary. Immunostaining with antibodies raised against .beta.-TSH, .beta.-FSH and .alpha.-endorphin were observed in scattered cells. Those cells that contained immunoreactive .alpha.-endorphin did not appear to contain .alpha.-subunit. The ultrastructural features of adenoma cells showed no resemblance to any known cells in nontumorous or tumorous pituitaries. Adenohypophyseal cells, after neoplastic transformation, may have the ability to secrete a number of biochemically unrelated hormones, suggesting that during embryonic development they pass through a common progenitor cell stage, capable of plurihormonal activity.