Sarcomatous variants of Wilms' tumor. Immunohistochemical and ultrastructural comparison with classical Wilms' tumor

Two cases of malignant rhabdoid tumor of the kidney (MRT) and two cases of bone metastasizing renal tumor (BMRT) were studied using electron microscopy and immunohistochemistry, in an attempt to evaluate the histogenetic relation to classical Wilms' tumor (2 cases). The two cases of MRT showed ultrastructural features of intermediate filament clusters in the cytoplasm. Vimentin, keratin, laminin, and peanut (PNA) lectin were immunohistochemically demonstrated in two cases of MRT. Tissue polypeptide antigen (TPA) was detected in one case. As for BMRT, the metastatic lesion exhibited numerous rosette-like structures of tumor cells. Vimentin was immunohistochemically demonstrated in one case, but no other antibodies were stained in two cases. Two cases of classical Wilms' tumor immunohistochemically demonstrated vimentin, keratin, PNA lectin, and TPA. MRT and BMRT fall within the broad spectrum of Wilms' tumors from the histogenetic aspect, but their clinical behavior is distinct.