Imaging Characteristics of Nephrogenic Rests Versus Small Wilms Tumors: A Report From the Children’s Oncology Group Study AREN03B2

Sandberg JK, Chi YY, Smith EA, Servaes S, Hoffer FA, Mullen EA, Perlman EJ, Tornwall B, Ehrlich PF, Geller JI, Grundy PE, Fernandez CV, Dome JS, Khanna G. Imaging Characteristics of Nephrogenic Rests Versus Small Wilms Tumors: A Report From the Children’s Oncology Group Study AREN03B2. AJR Am J Roentgenol. 2020 May;214(5):987-994. doi: 10.2214/AJR.19.22301. Epub 2020 Mar 11. PubMed PMID: 32160052; PubMed Central PMCID: PMC7756929.

Distinguishing nephrogenic rests from small Wilms tumors can be challenging. This retrospective study was performed to determine if imaging characteristics can be used to distinguish nephrogenic rests from Wilms tumors. All cases of pathologically confirmed nephrogenic rests and Wilms tumors smaller than 5 cm in maximum dimension on imaging in patients younger than 5 years old were identified from the Children’s Oncology Group AREN03B2 study (July 2006–August 2016). Exclusion criteria were chemotherapy before pathologic evaluation or more than 30 days between imaging and surgery; in addition, patients with nephrogenic rests occurring within or juxtaposed to a Wilms tumor and patients with diffuse hyperplastic perilobar nephroblastomatosis were excluded. Two radiologists who were blinded to pathology results assessed all lesions. The two-sample t test was used for continuous variables, and the Fisher exact test was used for categoric variables. ROC analysis was performed to determine the optimal size cutoff for distinguishing between nephrogenic rests and Wilms tumors.