PITUITARY-ADENOMAS - AN IMMUNOHISTOCHEMICAL STUDY OF HORMONE PRODUCTION AND CHROMOGRANIN LOCALIZATION

Abstract

Tumors from 42 surgically resected pituitaries and from 13 [human] autopsy cases were studied immunohistochemically with polyclonal antisera to 7 anterior pituitary hormones, and with a newly developed monoclonal antibody directed against human chromogranin for evaluation of the distribution of chromogranin in normal and neoplastic pituitaries. In addition, a prospective study was done for assessemnt of the prevalence, morphology and endocrine cell types of pituitary tumors in 100 autopsy subjects. When these 55 pituitary adenomas was examined with monoclonal antibody (LK2H10) directed against human chromogranin, selective staining of normal adenohypophyseal cell types and pituitary tumors was observed. Most null-cell adenomas (12/14) were positive for chromogranin, whereas all prolactin (PRL)-producing adenomas (19/19) were negative. Growth hormone (GH) adenomas were focally positive (9/9). All oncocytomas (2/2), 1 thyrotropin (TSH) adenoma, and a follicle-stimulating hormone/luteinizing hormone adenoma were positive for chromogranin. One or more adenomas were present in 14% of the autopsy cases. The tumors occurred most frequently in patients in the 5th through the 7th decades of life. Immunohistochemical staining of 13 adenomas revealed 1 TSH, 1 ACTH and 4 PRL-producing tumors, whereas 7 other tumors, which were null-cell or undifferentiated adenomas, failed to stain for any of the 7 principle pituitary hormones. Antibody LK2H10 to human chromogranin apparently is useful in the immunohistochemical characterization of pituitary adenomas. Incidental pituitary microadenomas from autopsy-derived pituitaries most commonly produce PRL, or they belong to the null-cell or undifferentiated tumor group.