Hemangiosarcomas in Intercostal Brown Adipose Tissues of the Sternum Induced by Urethane in TgrasH2 Mice

Urethane has been used as a positive control material for carcinogenicity studies in the TgrasH2 mouse that is a valuable model in pre-clinical safety investigations. This article describes the incidence of hemangiosarcomas (HSAs) in the intercostal sternal brown adipose tissue that is routinely collected along with the sternum following the administration of 1000 mg/kg urethane to a total of 230 TgrasH2 mice (115 mice/sex). We report that HSAs were observed in 27/115 (23.48%) males and 17/115 (14.78%) females in the intercostal brown adipose tissue of the sternum, which was the third most common tissue in which these findings were observed, following the spleen (100/115 [86.96%]) in males and (90/115 [78.26%]) in females and lungs (30/115 [26.09%]) in males and (23/115 [20.00%]) in females. The rare investigations of HSAs in brown adipose tissue highlight unusual locations where the elevated incidence of HSA is observed, which is important when performing histopathological evaluation in the context of a pre-clinical carcinogenicity study.