Validation of the Modified Bosniak Classification System to Risk Stratify Pediatric Cystic Renal Masses: An International, Multi-Site Study from the Pediatric Urologic Oncology Working Group of the Societies for Pediatric Urology
Leslie Peard, MD1, Patricio Gargollo, MD2, Campbell Grant, MD3, Andrew Strine, MD3, Manon de Loof, MD4, Celine Sinatti, MD4, Anne-Francoise Spinoit, MD, PhD4, Piet Hoebeke, MD, PhD4, Nicholas Cost, MD5, Alexandra Rehfuss, MD6, Seth Alpert, MD6, Amanda Saltzman, MD1.
1University of Kentucky, Lexington, KY, USA, 2Mayo Clinic, Rochester, MN, USA, 3Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA, 4Ghent University Hospital, Gent, Belgium, 5Children's Hospital of Colorado, Denver, CO, USA, 6Nationwide Children's Hospital, Columbus, OH, USA.
BACKGROUND: Pediatric cystic renal lesions are challenging to manage as little is known about their natural course. A modified Bosniak classification system has been proposed for risk stratification, but literature validating this system remains limited. This study’s objective was to determine if the modified Bosniak classification system correlates with pathologic diagnoses.
METHODS: Patients treated for cystic renal masses between 2000 and 2019 from five institutions with available imaging and pathology were identified. Clinical characteristics and pathology were obtained retrospectively. Characteristics from the most recent ultrasound (US), computed tomogram (CT), and/or magnetic resonance films (MRI) were recorded. Reviewers assigned a modified Bosniak classification to each scan. Modified Bosniak scores 1/2 were considered low-risk and 3/4 high-risk. These groups were compared with pathology (benign, intermediate, malignant). Agreement between imaging modalities was also explored.
RESULTS: 99 patients were identified. Table 1 summarizes the relationship between modified Bosniak class and pathology. Malignant and intermediate pathologies were classified as high-risk on imaging with a sensitivity of 84%, specificity of 81%, positive predictive value of 85.7%. There was substantial agreement between US/CT (n=55; κ=0.66) and moderate agreement between US/MRI (n=20; κ=0.52) and CT/MRI (n=13; κ=0.47).
CONCLUSIONS: Pediatric cystic renal lesions assigned modified Bosniak class 1/2 are mostly benign, whereas class 3/4 lesions are likely intermediate or malignant pathology. However, due to a significant misclassification rate, 16% of malignant lesions would be missed if observed based on the modified Bosniak system alone. Therefore, other clinical characteristics remain important for operative decision-making. There is substantial agreement between US and CT when evaluating pediatric cystic renal lesions.
| Benign | Intermediate | Malignant | p=value | |
| 1 | 25 | 1 | 1 | |
| 2 | 9 | 6 | 1 | |
| 3 | 5 | 9 | 1 | |
| 4 | 3 | 2 | 36 | <0.001 |
| 1/2 | 34 | 7 | 2 | |
| 3/4 | 8 | 11 | 37 | <0.001 |
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