Pediatric Small Renal Masses: Can Tumor Size Predict Histology and the Potential for Nephron-Sparing Surgery?

The majority of children with unilateral renal masses (uRM) suspicious for malignancy undergo radical nephrectomy (RN), while nephron-sparing surgery (NSS) is reserved for select cases. We investigated the impact of tumor size (TS) on the probability of histology. We hypothesized that pediatric small renal masses (pSRM) are more likely benign or non-Wilms tumor (WT), thus potentially appropriate for NSS.

The Surveillance, Epidemiology, and End Result (SEER) database was analyzed for patients aged 0-18 years diagnosed with a uRM from 2000-2016. Statistical analysis was performed to help determine a TS cut-point to predict WT and assess the predictive value of TS on WT histology. Additionally, a retrospective review was performed of patients 0-18 years old who underwent surgery for a uRM at a single institution from 2005-2019. Statistical analysis was performed to assess the predictive value of TS on final histology.

From the SEER analysis, 2,016 patients were included. 1,672 (82.9%) tumors were WT. Analysis revealed 4 cm to be a suitable cut-point to distinguish non-WT. Tumors ≥4 cm were more likely WT (OR 2.67, P≤.001), but this was driven by the statistical significance in children 5-9 years old. From the institutional analysis, 134 patients were included. Ninety-seven (72.3%) tumors were WT. Tumors ≥4 cm had higher odds of being WT (OR 30.85, P = .001), malignant (OR 6.75, P = .005), and of having RN-appropriate histology (OR 46.79, P<.001).

The probability that a pediatric uRM is WT increases with TS. Four cm is a logical cut-point to start the conversation around defining pSRMs and may help predict NSS-appropriate histology.

The Journal of urology. 2022 Nov 29 [Epub ahead of print]

Daniel S Han, Jonathan P Walker, Andrew Nicklawsky, Peter Boxley, N Valeska Halstead, Michael Tonzi, Sarah L Hecht, Alyse Staley, Megan Eguchi, Myles G Cockburn, Jonathan P Roach, Amanda F Saltzman, Nicholas G Cost

Stanford University School of Medicine and Lucile Packard Children's Hospital, Palo Alto, California., University of Tennessee College of Medicine Chattanooga, Chattanooga, Tennessee., University of Colorado Cancer Center, Aurora, Colorado., University of Colorado School of Medicine and Children's Hospital Colorado, Aurora, Colorado., Oregon Health and Sciences University, Portland, Oregon., University of Southern California, Keck School of Medicine, Los Angeles, California., Surgical Oncology Program of the Children's Hospital Colorado, Aurora, Colorado., University of Kentucky College of Medicine, Lexington, Kentucky.