[Histology, fine structure and differentiation of experimental Wilms tumors (author's transl)].

: Histologic studies indicate that the cycasin-induced Wilms' tumor in the rat is equal to human nephroblastoma in appearance. Therefore, it may represent an interesting system for experimental oncology. In electron microscopy, the spindle cells of the sarcoma region mostly represent tubular cells. Besides, the author's results showed that preexisting mesenchyma cells and blood vessels also form part of the tumor. Electron microscopy studies have shown that cycasin feeding will lead to early cellular changes indicating that cycasin exercises a nucleotoxic effect. Present results do not favor the dysontogenic concept of the formation of Wilms' tumor, since this tumor can be induced diaplacentally.