The incidence of neoplasms in Syrian hamsters with particular emphasis on intestinal neoplasia.

The incidence of neoplasms is presented for 600 Syrian hamsters (Mesocricetus auratus) used as controls in the evaluation of carcinogenicity of various experimental viral vaccines administered as a single subcutaneous injection at birth. Approximately 30% of the animals had neoplasms with no appreciable sex difference in the overall tumor incidence. The most frequent tumor types were those of the adrenal cortex (13.5%), the lymphoreticular system (3%), and the endometrium (3%). Small intestinal adenocarcinomas occurred in 0.8% of the animals. In this laboratory, the incidence of intestinal tumors is greater and more variable than that in the mouse or the rat. Furthermore, several unusual morphologic and biologic features of this tumor type were identified. These findings raise questions about the suitability of the Syrian hamster in carcinogenic bioassays.