Abstract
Immunohistochemical techniques and electron microscopy were employed in a study of nine surgical patients with nonfunctioning pituitary adenomas and no clinical or biochemical evidence of increased hormone secretion. Six of the patients were found to have gonadotroph adenomas, which exhibited extensive immunostaining for gonadotropins, and the remaining three appeared to have null cell adenomas, which showed no reactivity for any pituitary hormone. Clinically, it was difficult to distinguish these two groups of patients. Gonadotroph adenomas are likely to have low secretory activity, resulting in normal or slightly high serum gonadotropin levels. In addition, some common histopathological features were observed in the two groups: a predominantly papillary, sinusoidal pattern; rather poorly developed cell organelles, with the exception of an abundance of mitochondria; and small, round secretory granules dispersed throughout the cytoplasm. It is possible that null cell adenoma produces so little gonadotropin that it is not detectable by immunohistochemistry. In this study, two thirds of the nonfunctioning adenomas were, in fact, gonadotroph adenomas. The authors speculate that there is a common cytogenesis of gonadotroph adenomas and some, if not all, null cell adenomas.
