NEOPLASTIC AND HYPERPLASTIC LESIONS IN AGING C3H HEJ MICE/

The C3H/HeJ inbred mouse strain is commonly used in biomedical researc h. An important feature of inbred mouse strains, such as C3H/HeJ, is t he propensity to develop a limited variety of neoplasms, the morpholog ic features of which are remarkably similar between individual animals Necropsies of 864 C3H/HeJ female and male mice, ranging in age from 1 0 days to two years, revealed 16 types of neoplastic (mammary. liver, ovarian, adrenocortical, and other less frequent neoplasms) and three types of hyperplastic (luteal cell hyperplasia, cystic endometrial hyp erplasia, and pancreatic islet hyperplasia) diseases. Most of the tumo rs were first observed at 10-12 months of age and increased in frequen cy as mice aged. Ovarian tumors, mammary adenocarcinoma, hepatocellula r adenoma, and cystic endometrial hyperplasia were the most frequent l esions in female mice. Hepatocellular adenoma, adrenocortical adenoma, and pancreatic islet hyperplasia were the most common lesions in male mice. Coincidence of hepatocellular adenoma, adrenocortical adenoma, and pancreatic islet hyperplasia in male C3H/HeJ mice, and of ovarian tumors? mammary adenocarcinoma, and cystic endometrial hyperplasia in female mice were statistically significant. The most common tumors obs erved in this study remain the types originally described for the C3H/ HeJ strain, despite long term inbreeding and changes in husbandry cond itions. These data on tumor types occurring in the C3H/HeJ inbred mous e strain are valuable as baseline information for interpretation of dr ug safety studies and for characterization of new spontaneous or induc ed mutations.