Spontaneous renal neoplasms in aged Crl:CDBR rats

Primary neoplasms of the kidneys occurred in 11/682 male (1.6%) and 2/694 female (0.3%) Crl:CDBr strain Sprague-Dawley rats. Eight of 13 neoplasms were of mesenchymal origin and 5 of 13 were epithelial. Five neoplasms were lipoma (3) or liposarcoma (2). Three of 13 were either hemangioma (1) or mesenchymal tumors (2). The epithelial neoplasms were carcinomas. There was no microscopic evidence of metastasis among those neoplasms judged malignant on morphologic criteria. The overall natural incidence in males was nearly double that compiled for this strain while in females the incidence was similar to that reported for other females.