Studies on the histogenesis of experimentally induced yolk sac tumor in rats

As a method to elucidate the histogenesis of this tumor, it is necessary to make a comparative study of the morphological relation between the histopathology of the tumor and the mother tissue which is considered to be the origin of the tumor. Therefore, as already reported, since we induced the yolk sac tumor by treating the fetal membrane of pregnant rats with carcinogenic agents, we have comparatively studied the tumor tissue and the fetal membrane, which is considered the mother tissue, to elucidate the histogenesis by seeking the similarity between them and the common features and obtained the following conclusions. First, the presence of PAS positive non-glycogenic granules was noted in both cytoplasms, and then the localization of AFP was confirmed in both cytoplasms also in the study with a fluorescence antibody method using anti-rat AFP antibody. Further, in the observation at the level of electron microscopy, as findings common to both, we noted the presence of round homogeneous non-structural substance and characteristically developed r-ER, and, on the other hand, immature nuclei containing thread-like nucleolonema, considered characteristic to germ cell tumor. From the above results, this induced tumor was considered to have developed from the rat fetal membrane as mother tissue.