Suprasellar peri-infundibular ectopic adenohypophysis in fetal and adult brains.

Ectopic anterior pituitary cells, identified by histological, electron microscopic, and immunohistochemical methods, were consistently found in the leptomeninges of the suprasellar peri-infundibular region of fetal brains. The cell groups were not in continuity with the pars tuberalis of the adenohypophysis. Suprasellar peri-infundibular ectopic pituitary cells, which showed no neoplastic character, were found in 15 of 20 "normal" adult brains that were similarly examined. This finding sheds new light on the possible origin of intracranial ectopic pituitary adenomas.