[Ultrastructural and immunocytochemical study on human silent pituitary adenomas].

16 cases of silent pituitary adenomas were studied with immunoelectron microscopy using protein A-gold probes and were subtyped on their ultrastructural appearances and immunocytochemical reactivity. 2 cases were identified as sparsely granulated PRL adenomas, comprising numerous PRL-positive cells. In 2 acidophil stem cell adenomas were detected GH- and PRL-producing cells, though fewer in number. No hormone activity was found in the secretory granules of 3 oncocytomas and 9 undifferentiated cell adenomas. The morphological features of various silent pituitary adenomas are described and their clinical implications are discussed.