Histopathological and immunohistochemical features of proliferative lesions in the pituitary pars distalis of rats

• Published in: Journal of Toxicologic Pathology Vol. 34; no. 1; pp. 1 - 9
• Main Authors: Doi, Takuya, Kanno, Takeshi, Sato, Junko
• Format: Journal Article
• Language: English
• Published: Japan JAPANESE SOCIETY OF TOXICOLOGIC PATHOLOGY 01.01.2021; The Japanese Society of Toxicologic Pathology; Japan Science and Technology Agency; Japanese Society of Toxicologic Pathology
• Subjects: adenoma; Brain tumors; Carcinogenicity; Carcinogens; Carcinoma; Concise Review; Females; focal hyperplasia; Growth hormones; Lesions; pars distalis; Pituitary; Prolactin; rat; Rodents; Tumors; focal hyperplasia; pituitary; adenoma; rat; carcinoma; pars distalis
• ISSN: 0914-9198; 1881-915X; 1347-7404
• DOI: 10.1293/tox.2020-0050

Pituitary proliferative lesions derived from the endocrine cells of the pars distalis are frequently encountered and adenomas/carcinomas are a common cause of death in standard 2-year carcinogenicity studies using various rat strains, especially Sprague-Dawley. This report describes the immunohistochemical characteristics of pituitary tumors derived from the pars distalis in rats. Prolactin (PRL)-containing tumors are the most common, with PRL/growth hormone (GH) dual positive tumor masses (PRL/GH co-positive tumor masses) being more prevalent than only PRL-positive tumor masses (PRL single-positive tumor masses). GH-containing tumors are relatively numerous and many of these are also PRL/GH co-positive tumor masses. TSH-containing tumors are common in females. PRL-containing tumors have been shown to increase the incidence of hyperlactation in males and mammary adenomas/adenocarcinomas in females, suggesting that these masses are functional tumors.