A uterine choriocarcinoma in a virgin Donryu rat.

A uterine choriocarcinoma was found in a 49-wk-old virgin Donryu rat given intrauterine administration of N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG). The tumor was macroscopically present as a bloody cystic mass and microscopically composed of 2 kinds of cells: small basophilic cells similar to cytotrophoblasts in the rat placenta and large cells with big nuclei resembling giant trophoblasts. The giant cells were positive for 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), although immunohistochemical examination was negative or nonspecific for chorionic gonadotrophins, including beta human chorionic gonadotrophin (beta hCG), human placental lactogen (hPL), and placental glycoprotein (SP-1), or for placental alkaline phosphatase (ALP). However, the animal exhibited a slight mammotropic status. The results thus suggest a choriocarcinoma nature for this uterine tumor and that the tumor cells secrete a weakly mammotrophic hormone.