Embryo-derived teratocarcinoma. II. Teratocarcinogenesis depends on the type of embryonic graft.

Early post-implantation mouse embryos or their embryonic and extraembryonic portions were transplanted under the kidney capsule of adult isogenic recipients in order to test the tumor-producing potential of various grafts and to establish the optimal conditions for teratocarcinoma production. The highest yield of malignant tumors was obtained from 7-day embryos transplanted in toto. Severing the extraembryonic portion of 7-day egg cylinders prior to transplantation of the embryonic part reduced the number of teratocarcinomas to values comparable with those obtained from transplanted 6-day embryos. The extraembryonic portion of 7-day embryos produced no tumors. These data suggest that extraembryonic portions of the 7-day egg cylinder do not have tumorigenic potential alone, but may increase the yield of teratocarcinomas from the embryonic portion of the egg cylinder.