[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, precise mechanisms of induction and pathogeneses of these tumors still remain unknown. The present study was undertaken in order to elucidate whether this phenomenon is common to all rodents, to identify the origin of these tumors and 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 and alpha-FP suggested that the malignant tumors belonged to the category of yolk sac tumors. Similarities of 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 yolk sac tumors disclosed that the tumor was composed of clones with XX and XY sex chromosome constitution. The 1P+marker chromosome was identified as a consistent abnormality, which seemed to play an important role for the development of yolk sac tumors in chinese hamsters.