Pituitary neuroendocrine tumors and granular cell pituicytomas at autopsy: Incidence, cell types, locations, and histogenesis in 150 pituitary glands

ABSTRACT Objectives The incidence of pituitary neuroendocrine tumors has been reported high at autopsy. This study aimed to detect many tumors in both anterior and posterior lobes to prove tumor histogenesis. Methods In total, 150 pituitary glands were studied from the University of Kansas Medical Center from 1995 to 2000. The pituitary gland was sagittally sliced from anterior to posterior into 6 to 8 sections. When H&E-stained sections revealed tumors, the tumors were immunohistochemically stained for 6 pituitary hormones. Results Among 150 autopsy cases, 38 (25.3%) harbored microadenomas, including 4 cases with double tumors. Twenty-three (54.7%) cases were negative to all pituitary hormones. Of the remaining 19 tumors, 13 (30.9%) were lactotrophs, with 4 cases being concomitantly somatotrophs and gonadotrophs, and 2 cases were corticotropes. More than 85% of pituitary neuroendocrine tumors were adjacent to the capsule. Thirteen (8.7%) granular cell pituicytomas were found in the posterior lobe. There were pituicytes transforming into granular cell tumors. Conclusions The incidence was 25.3% for pituitary neuroendocrine tumors and 8.7% for granular cell pituicytomas. Since most pituitary neuroendocrine tumors were adjacent to the pituitary capsule, the capsule appeared to be the germinal center. Both pituitary tumors belonged to the 2 different transcription factor lineages.