Abstract
Fifteen pituitary adenomas with hyperprolactinemia obtained at surgery were studied by an indirect immunoperoxidase technique for the demonstration of prolactin. (Anti-human prolactin was supplied by NIAMDD.) The immunoreactive prolactin was revealed in the cytoplasm of the tumor cells in 13 cases, which were classified into two types according to the population of prolactin cells and the intracytoplasmic localization of immunoreactive prolactin.
Type I—8 cases—
The adenomas of this type consisted of numerous prolactin cells, which accounted for more than 90% of the tumor cells. These were strongly suggested to be the primary prolactin producing adenomas. Immunoreactive prolactin was characteristically found in the form of ‘Nebenkern’ in the cytoplasm of these adenoma cells, while it distributed evenly throughout the cytoplasm in normal prolactin cells. This finding suggested discrepancy of the hormone syntheses between normal and neoplastic prolactin cells. Clinically, serum prolactin levels were over 1, 000 ng/ml, and the tumor sizes were variable from intrasellar types to larger ones showing remarkable suprasellar extensions.
Type II—5 cases—
The proportion of prolactin cells was only 10 ?? 30% of the tumor cells, which also contained growth hormone and/ or luteinizing hormone in two cases. These adenomas, consisting of prolactin cells and some other cell types, might be considered to show the ‘chimera’ like proliferation. In contrast with Type I, intracytoplasmic immunoreactive prolactin was detected unevenly in each prolactin cells. Clinically, serum prolactin levels were about 100 ng/ml, and all the tumors of this type showed moderate or marked suprasellar extensions. From this viewpoint, the interruption of prolactin inhibiting factor (PIF) might play some role to activate prolactin cells of these adenomas. Since the immunohistochemical findings well reflected the serum prolactin levels in most cases, it might be considered that the origin of hyperprolactinemia can be attributed to the tumor itself.
