Angioma-like pseudometamorphosis in Wilms' tumors subjected to preoperative radio- and chemotherapy.

Six Wilms' tumors (stage III-V), which had undergone preoperative irradiation and chemotherapy, were examined histologically. While mesenchymal and differentiated epithelial tumor elements were preserved to a large extent, blastemic tumor structures were almost completely lacking. Instead, pseudoangioma-like structures similar to cavernous hemangioma prevailed. As demonstrated by transitional pictures, the pseudoangioma-like pattern is a result of the fact that blastemic tumor elements are replaced by blood after therapy-induced necrosis and lysis. The clinical advantages of preoperative treatment are briefly discussed, especially for patients with advanced tumors.