Trophoblastic and mesenchymal structures in rat yolk sac carcinoma.

The presence of trophoblastic and mesenchymal structures in primary as well as in transplanted rat yolk sac carcinomas (YSC) is described. These structures were only recorded in rat yolk sac carcinomas derived from displaced yolk sac but never in embryo-derived yolk sac carcinomas. It is suggested that the endodermal carcinoma cells displaying either a parietal or a visceral yolk sac pattern as well as the mesenchymal and trophoblastic structures may have a common cell ancestor.