Nonneoplastic lesions of the ovary in Fischer 344 rats and B6C3F1 mice.

The National Toxicology Program's pathology database on 2-year carcinogenicity studies was reviewed for nonneoplastic ovarian disease. Ovaries from 39,941 female Fischer rats and 41,444 female B6C3F1 mice were examined. A variety of inflammatory, degenerative, vascular, and proliferative lesions were documented and are described. The most common ovarian lesions in rats were cysts (6%). The most frequent ovarian lesions in mice were cysts (15%), acute inflammation (4%), degeneration (4%), vascular disease (2.5%), and atrophy (2%). There was no difference in incidence of ovarian disease between controls and treated animals. The frequency of ovarian disease in mice exceeded the frequency in rats in every category.