Histogenesis of yolk sac carcinoma induced by fetectomy in the rat.

Pregnant rats whose fetuses were removed on the 12th day of gestation developed tumors dysontogenetically. Out of 127 operated rats, 103 rats gave rise to tumors, which were histologically yolk sac carcinomas (52 cases), adenocarcinomas (34 cases), choriocarcinomas (8 cases) and teratomas (74 cases). Induction of malignant tumors was dependent on the male rats used for mating and the time of fetectomy. Killing of primordial germ cells by low-dose irradiation before fetectomy decreased the occurrence of tumors. These findings indicate that malignant tumors, including yolk sac carcinoma, might be of germ cell origin.