Evaluation of effect of preoperative chemotherapy on Wilms' tumor histopathology

Purpose: To evaluate usefulness of cutting needle biopsy (CNB) to recognize pediatric renal tumors and to predict the evolution of histology during preoperative chemotherapy of Wilms tumors. Methods: Ninety pediatric patients were operated for renal tumors at our institution in 1988-2015. We included all 64 patients who had undergone CNB at diagnosis and whose CNB and nephrectomy samples were available for re-evaluation. Results: The CNB was diagnostic in all 59 Wilms tumors but only in two out of live non-Wilms tumors. Anaplasia was missed by CNB in one of three with diffuse anaplasia in nephrectomy specimens. In Wilms tumors the proportions of the blastemal, stromal and epithelial components were 55% (IQR 25-85), 28% (IQR 10-58) and 2% (IQR 0-10) in CNB samples and 5% (IQR 0-64), 15% (IQR 0-50) and 15% (IQR 0-44) in the nephrectomy specimens (p-values 0.002,0.599 and 0.005 respectively). The degree of tumor necrosis was in median 80% (IQR 21-97), after preoperative chemotherapy. The degree of tumor necrosis after chemotherapy had a positive correlation with the proportion of blastemal component (p = 0.008) and a negative correlation with proportion of epithelial component in pre-chemotherapy CNB samples (p