Ultrastructural and Immunoelectron Microscopical Study of Human Pituitary Somatotroph Adenomas and Prolactinomas

Nowdays the application of immunohistochemical techniques and ultrastructuralanalysis and correlation with clinical and biochemical findings have led to a moredetailed functional classification,in which growth hormone (GH)-producing andprolactin (PRL)-producing adenomas have been shown to comprise more than halfof pituitary adenomaso.Few immunoelectron microscopic studies on GH and PRLadenomas have been made,however,in limited cases so far,though a numberof authors have described the characteristics of pituitary adenomas by conventionalelectron microscopy.In addition to routine electron microscopy,immuno-.electron microscopical technique using protein A-gold probes was applied in

17 cases of pituitary somatotroph adenomas and 38 cases of prolactino- mas were studied with electron microscopy and immunoelectron microscopy using protein A- gold complex.4 adenomas were confirmed by immunoelectron microsco- py simultaneously containing growth hormone (GH)-and prolactin (PRL)-ploduc- lag cells.6 cases were classified as densely granulated GH adenomas and 11 as sparsely granulated variant,whereas only 3 adenomas out of 38 prolactinomas were identified as densely granulated adenomas.The study showed that all cells with fibrous bodies did not possess the secretory granules positive for GH and in some cells with fibrous bodies PRL-producing granules were detected.Misplaced exocylo sis was found freqently in the sparsely granulated prolactinomas.It was suggested that fibrous bodies might not be a morphological feature to demonstrate distinctively in pituitary somatotroph adenomas.