Immunocytochemical localization of synaptophysin in human hypophyses and pituitary adenomas

Synaptophysin (SYP) was demonstrated in the cytoplasm of somatotrophs, lactotrophs, thyrotrophs, and gonadotrophs by the avidin-biotin-peroxidase complex method using a monoclonal antibody (SY38). Some adenohypophysial corticotrophs, most corticotrophs spreading to the posterior lobe, and Crooke's hyaline material did not immunoreact with anti-SYP. In the neurohypophysis, nerve fibers and pituicytes were immunopositive. Most pituitary adenomas, including null cell adenomas, immunostained with SYP. The presence of SYP could not be correlated with hormone content, cytoplasmic granularity, and clinical symptoms. Neuron-specific enolase was expressed with SYP in most adenomas, whereas chromogranin was present only in a few tumors. Although SYP cannot be used as a general marker to identify specifically pituitary cells or adenomas, its demonstration may be helpful in immunocytochemical characterization of some null cell adenomas.