Pathology of pituitary adenomas.

A new pituitary classification has been developed, based on the histologic, histochemical, immunocytologic and electron microscopic investigation of 207 pituitary adenomas removed surgically from male and female patients of various ages and different clinical symptomatology. Based principally on cytogenesis, the classification attempts to correlate the morphologic features of the tumor cells with their secretory activities, the clinical history, symptomatology, and biochemical findings. The classification consists of the following eight entities: 1) growth hormone cell adenoma; 2) prolactin cell adenoma; 3) mixed growth hormone cell-prolactin cell adenoma; 4) acidophil stem cell adenoma; 5) corticotroph cell adenoma; 6) thyrotroph cell adenoma; 7) gonadotroph cell adenoma; 8) undifferentiated cell adenoma, including oncocytoma. Prolactin adenomas were found to be the most frequently occurring pituitary adenoma type.