Abstract
The incidence, nomenclature, and diagnostic criterion of spontaneous tumors of the pituitary and adrenal glands in rats and mice were reviewed. From these reviews, diagnostic problems on these proliferative lesions encountered sometimes in routine long-term toxicity and carcinogenicity studies were pointed out. In these organs, the main diagnostic problems were the difficulty to differentiate between focal hyperplasia and small adenoma and to separate carcinoma from adenoma. Most of these problems might be due to the fact that the biological features of these proliferative lesions were not completely clarified in these animals. Criteria in the differential diagnosis proposed in the literature, therefore, seemed to be somewhat arbitrary. More practical methodology for adequate histopathological evaluation was discussed on the carcinogenicity of endocrine organs.
