Aging changes in CD-1 HaM/ICR mice reared under standard laboratory conditions.

Three hundred CD-1 HaM/ICR mice were observed for 2 years, and useful necropsies were done on 99 males and 102 females. Mortality was 50% at 16 months in the males and 18 months in the females. Among mice that came to autopsy, total tumor incidence was 54% for males and 75% for females, with most neoplasms occurring after 18 months. Adenomas or adenocarcinomas of the lung were the most frequent, followed by lymphoreticular tumors, vascular tumors, hepatomas, subcutaneous fibrosarcomas, and adenocarcinomas of the mammary glands. Some degree of amyloidosis was seen in half the mice of both sexes, beginning at 8 months in males and 12 months in females. Variability in tumor incidence among small groups if mice emphasized the need for adequate samples.