A Pathological Study on Spontaneous Hepatic Neoplasms in BDF1 Mice

Neoplastic and proliferative hepatic lesions observed in 500 male and 499 female DBF1 mice used as untreated controls in the past ten 2-year carcinogenicity studies (each 50 males and 50 females for one study) for industrial chemicals at the Japan Bioassay Research Center. The incidences of altered cell foci (ACF) were 11.6% in males and 2.8% in females and those of each type of ACF were as follows; basophilic, eosinophilic, clear, vacuolated, and mixed cell foci were 4.0%, 1.2%, 4.6%, 0.2%, and 1.6% in male mice, respectively, and 1.2%, 0%, 0.8%, 0.4%, and 0.4% in females, hepatocellular adenoma (HCA) was 15% in males (minimum 4%, maximum 30%), and 4.4% in females (minimum 2%, maximum 8%), hepatocellular carcinoma (HCC) was 22.8% (minimum 2%, maximum 36%) in males and 2.0% (minimum 0%, maximum 4%) in females, vascular tumors were 6.6% (minimum 0%, maximum 6%) in male mice and 15.0% (minimum 6%, maximum 20%) in females. Compared with the data in rats, incidences of HCA and HCC in BDF1 mice were remarkably higher, however, the incidence of ACF in BDF1 mice was lower than those of rats. The different incidence of ACF noted in rats and in mice may suggest the different implications of ACF as the preneoplastic role in hepatocarcinogenesis.