[Experimental induction and cytogenetic study of yolk sac tumors in Chinese hamsters]

The development of teratomas and yolk sac tumors from displaced yolk sac is well documented in rats and mice. However, the precise mechanisms of induction and pathogeneses of these tumors still remain unknown. The present study was undertaken in order 1) to elucidate whether this phenomenon is common to all rodents, 2) to identify the origin of these tumors and 3) to explore specific chromosomal changes in yolk sac tumors. Ten benign teratomas and two malignant tumors with teratomatous elements were obtained from 33 Chinese hamsters after fetectomy, followed by displacement of yolk sac. The histological characteristics and the presence of laminin in the stroma suggested that the malignant tumors belonged to the category of yolk sac tumors. Similarities in electromicroscopic features observed in the tumor cells and the yolk sac of normal 12-day conceptuses suggested that the tumor originated from yolk sac cells. Chromosomal analyses of in vitro cell lines established from one of the yolk sac tumors disclosed that the tumors was composed of clones with an XX and XY sex chromosome constitution. The 1p + marker was identified as a consistent abnormality, which seemed to play an important role in the development of yolk sac tumors in Chinese hamsters.