High incidence of spontaneous cervical and vaginal tumors in an inbred strain of Brown Norway rats (BN/Bi).

The incidence of spontaneously occurring tumors of the cervix and vagina was unusually high in an inbred strain of Brown Norway rats (BN/Bi). Fifty-four tumors were diagnosed in the cervixes or vaginas of 252 rats. Of the tumors, 7 were squamous cell carcinomas, 4 were leiomyomas, and the rest were sarcomas. These tumors were found in nearly 20% of all female rats that died naturally.