Intrasellar neural-adenohypophyseal choristoma. A morphological and immunocytochemical study.

A patient with mild acromegaly had recurrence of symptoms and signs of a chiasmal-area lesion seventeen years after radiation therapy for a presumed pituitary adenoma. A mass was found anterior to the pituitary gland. Abnormal tissue removed from the sphenoid sinus and sella turcica consisted of a predominantly ganglion-cell lesion. A few ganglion cells were immunoreactive for somatostatin. There were some small cysts lined by cells with immunostaining for glial fibrillary acidic protein, growth hormone or prolactin. Some cells with vacuoles and eosinophilic granules showed immunostaining for growth hormone, prolactin, ACTH, and beta-endorphin and, thus, appeared to be of adenohypophyseal origin. Cases of intrasellar ganglion-cell lesions have been reported, most of them associated with pituitary adenomas and acromegaly. The findings in this case are discussed in relation to the hypothesis that displaced, hypothalamic-type ganglion cells may produce a growth hormone-releasing factor that stimulates the development of a growth hormone-secreting pituitary adenoma. An alternative hypothesis is suggested that includes this concept, but also allows for the influence of non-neuronal cells on neuronal differentiation and for the possible influence of adenohypophyseal hormones on the replication of hypothalamic-type neurons in the lesion.