[An ultrastructural study of human ovarian yolk sac tumor--an investigation of its histogenesis compared to that of human yolk sacs (author's transl)].

Abstract

For the purpose of investigating the histogenesis of the yolk sac tumor, 7 cases of the tumor and 9 cases of human yolk sac were used. Histological, ultrastructural investigations together with immunofluorescent antibody examinations revealed the following results. Ultrastructurally yolk sac endodermal cells prior to the 7th week of pregnancy were proved to have microvilli, abundant glycogen which formed rosette, parallel arranged rough endoplasmic reticulum (rER), mitochondria closely associated with rER and ovoid electron dense amorphous granules which showed positive diastase-resistant PAS-reaction. Morphologically endoderm after the 8th week of pregnancy showed degenerative changes. Light microscopically the tumors showed Schiller-Duval body, endodermal sinus structure and clear-cells endoblastic pattern, but ultrastructurally the tumor cells of these three types showed approximately similar appearances. Ultrastructural features of the tumor seem to resemble those of the yolk sac endoderm before the 7th week of pregnancy. The tumor cells which form the epithelial mantling of Schiller-Duval body closely resembled the endodermal cells facing the yolk sac cavity with respect to the presence of abundant glycogen granules, rER, mitochondria, short irregular microvilli on the cell surface and remarkable nucleolus with thread-like nucleolonema. Both the tumor cells facing the endothelial cell and those which form the endodermal sinus structure and clear-cells endoblastic pattern resembled the endodermal cells facing the mesenchyma in view of the features of intracellular organelles, the presence of extracellular basement membrane-like substances and tubular structure.