Pathological Insights into Non-Neoplastic Renal Parenchyma in Wilms Tumor: Implications for Nephron-Sparing Surgery

Introduction This study aimed to evaluate the non-neoplastic renal parenchyma in Wilms tumor (WT) and investigate its impact on nephron-sparing surgery (NSS). Materials and Methods The non-neoplastic renal parenchyma of WT patients was prospectively collected for pathological examination. The histology of non-neoplastic renal parenchyma was assessed from two perspectives: nephrogenic rests (NRs) and nephrons. Results A total of 46 non-neoplastic renal parenchyma specimens were collected from 42 WT patients. The surgeons assessed the median proportion of non-neoplastic renal parenchyma as 30%, whereas using ellipsoid volume, it was calculated to be 27%. The Youden index of surgeons' assessment peaked at a 15% proportion of non-neoplastic renal parenchyma. The bilateral WT (BWT) group and NSS group exhibited significant differences compared with the unilateral WT group and radical nephrectomy group, respectively, with the BWT group showing a tendency toward thickened basement membrane. Conclusion The presence of NRs and endogenous nephron alternations should be given due attention in WT. The probability of abnormalities is low when the proportion of non-neoplastic renal parenchyma exceeds 15%, providing pathological support for expanding the adaptation of NSS.