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

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.