Entrapped, non-neoplastic adenohypophysiocytes in human pituitary adenomas

The immunoprofile of 76 human pituitary adenomas was studied with particular reference to the occurrence of entrapped, non-neoplastic pituitary cells. This phenomenon was defined as unevenly distributed, usually peripherally located cells forming less than 1% of the total cell population. The stellate contour of such passively incorporated cells departed from the more rounded shape of most principal, neoplastic cells. Thirty-six of the adenomas studied comprised one or more types of entrapped elements. According to the hormone produced, prolactin-(PRL-)cells most commonly occurred as a minor "foreign" component (seen in 23 of the adenomas), whereas growth hormone-(GH-) and adrenocorticotropic hormone-(ACTH-)cells rarely were trapped (seen in 5 and 4 of the adenomas. Entrapped follicle stimulating hormone-(FSH-), luteinizing hormone-(LH-), and thyroid-stimulating hormone-(TSH-)cells assumed an intermediate position (seen in 14, 17 and 15 of the adenomas, respectively).