Uterine tumors in old female mice exposed prenatally to diethylstilbestrol.

Pregnant strain CD-1 mice were treated with diethylstilbestrol (DES) or vehicle. Their female offspring were raised to old age and autopsied when terminally ill. Squamous metaplasia and adenomyosis were more common in uteri of these old mice exposed prenatally to DES than in control mice. Tumors of the uterine horns were seen in 17 of 143 DES-exposed mice and in 3 of 64 control mice. The controls had only leiomyomas, whereas 14 of the DES-exposed mice had adenocarcinomas. There were 5 cervical adenocarcinomas and 1 vaginal adenocarcinoma among treated mice but none in the control mice. Thus the effects of prenatal exposure to DES interacted with the effects of aging to produce a relatively high frequency of uterine adenocarcinoma.