Wilms tumor: the problem of diagnostic accuracy in children undergoing preoperative chemotherapy without histological tumor verification.

From 1989 to 1992, 9 consecutive children with a tentative diagnosis of Wilms tumor underwent therapy planned according to the International Society of Pediatric Oncology (SIOP)-9 Wilms tumor protocol, including preoperative chemotherapy. Because tumor biopsy is not recommended in this SIOP-9 protocol due to a possible tumor spread from open or needle biopsy, diagnostic accuracy is mandatory. We present our problems in diagnostic accuracy resulting in withdrawal of 2 children from preoperative chemotherapy, understaging the tumor in 2 and missing exact tumor histology due to complete tumor necrosis in 2. In addition, preoperative chemotherapy was applied in 1 child who later was found to have renal cell carcinoma. Although the SIOP-9 protocol of Wilms tumor treatment may be effective with regard to reducing the intensity of therapy, staging problems may be a major drawback in this therapeutic strategy based on preoperative chemotherapy.