PITUITARY-ADENOMA PRODUCING GROWTH-HORMONE AND ADRENOCORTICOTROPIN - A HISTOLOGICAL, IMMUNOCYTOCHEMICAL, ELECTRON-MICROSCOPIC, AND IN-SITU HYBRIDIZATION STUDY - CASE-REPORT

The authors report on the morphological features of a pituitary adenom a that produced growth hormone (GH) and adrenocorticotropic hormone (A CTH). This hormone combination produced by a single adenoma is extreme ly rare; a review of the available literature showed that only one pre vious case has been published. The tumor, which was removed from a 62- year-old man with acromegaly, was studied by histological and immunocy tochemical analyses, transmission electron microscopy, immunoelectron microscopy, and in situ hybridization. When the authors used light mic roscopy, the tumor appeared to be a bimorphous mixed pituitary adenoma composed of mio separate cell types: one cell population synthesized GH and the other ACTH. The cytogenesis of pituitary adenomas that prod uce more than one hormone is obscure. It may be that two separate cell s-one somatotroph and one corticotroph-transformed into neoplastic cel ls, or that the adenoma arose in a common stem cell that differentiate d into two separate cell types. In this case immunoelectron microscopy conclusively demonstrated ACTH in the secretory granules of several s omatotrophs. This was associated with a change in the morphological ch aracteristics of secretory granules. Thus it is possible that the tumo r was originally a somatotropic adenoma that began to produce ACTH as a result of mutations that occurred during tumor progression.