Spontaneous hepatocellular neoplasms and hepatic hemangiosarcomas in several strains of mice.

The incidence of spontaneous liver tumors, ratio of hepatocellular adenomas to carcinomas, degree of differentiation of hepatocellular carcinomas, and incidence of pulmonary metastases in several strains of mice from different experiments were examined. Hepatocellular tumors were rare in all strains before 12 months of age and then increased with age. They were more common in male than in female mice. Pulmonary metastases were rare before 24 months of age and occurred in 10 of 221 mice with hepatocellular carcinomas (4.5%); their incidence in different strains was not strikingly different. Hepatic vascular tumors were less common than hepatocellular tumors. No tumors of bile duct origin were observed in these mice.