SPONTANEOUS TUMORS IN F-344/Jcl RATS

The age-related incidence of spontaneously occuring neoplastic and non-neoplastic lesions in untreated F-344/Jcl rats, used as controls in carcinogenicity testing, were studied from the histological examination of tissues from 469 males and 354 females. The incidence of spontaneous tumors was 83.2% in the males and 71.2% in the females. The most common neoplasms were leukemia (males : 24.3%, females : 24.0%), pituitary adenoma (males : 16.0%, females : 45.2%), pheochromocytoma (males : 14.7% females : 7.3%, testicular interstitial cell tumor (males : 79.1%), and uterine endometrial stromal polyp(females : 16.4%). The incidence of other tumors of almost all the organs and/or tissues was low. Non-neoplastic lesions generally increased with advancing age of the animals.