Co-localization of honeycomb golgi and ACTH granules in a giant ACTH-producing pituitary adenoma

We document the co-localization of honeycomb golgi and ACTH-immunopositive granules in giant ACTH-producing pituitary adenoma cells. A 42-yr-old woman presented with Cushing's disease and a giant adenoma that invaded the sphenoid and cavernous sinus. She underwent transsphenoidal surgery followed by radiation therapy. Some of the adenoma cells were ACTH-positive and upon electron-microscopic (EM) study most were found to contain sparse granules and no type-I filaments. In many cells the golgi complex had undergone partial or total vacuolar transformation that resulted in the appearance of honeycomb golgi. Immunohistochemical study of mirror sections of portions containing cells with honeycomb golgi revealed that the cells with honeycomb golgi showed ACTH-immunopositivity. Honeycomb golgi, which was formerly considered a morphological marker of gonadotroph adenomas in females, has previously been identified in large ACTH-producing pituitary adenomas but there has been no direct evidence that individual cells with honeycomb golgi are cells that produce ACTH. Our immunohistochemical documentation of ACTH-immunoreactivity in individual adenoma cells containing honeycomb golgi clearly confirms that honeycomb golgi is not confined only to gonadotroph adenomas in females. Rather, the existence of honeycomb golgi in cells of other adenoma types may be due to their low hormone production and/or to disturbances in the regulation of the exocytotic pathway.