Uncommon Frequency of Adenocarcinomas of the Uterus in Virgin Han:Wistar Rats

In a longevity study on 320 male and 320 female specified-pathogen-free Han:Wistar rats, 119 (39.0%) of 305 females evaluated developed spontaneous metastatic uterine adenocarcinomas. These tumors caused a great difference between the mortality rates of males and females. Thirty five percent of the females died of adenocarcinomas of the uterus. The tumors began as small nodules in one or both horns near the bifurcation. Large tumors extended through the uterine wall and produced wide-spread transcoelomic metastases. Early lesions were well-differentiated adenocarcinomas but advanced tumors were more poorly differentiated.