Predicting malignant histology in small renal masses: the role of anatomical and radiological nephrometry scores

To evaluate the ability of anatomical nephrometry scoring systems to predict malignant histology in patients undergoing surgery for small renal masses (SRMs) ≤ 4 cm. Seventy-two patients with SRMs treated between January 2015 and March 2024 were retrospectively analyzed. Preoperative imaging was used to calculate eight nephrometry scoring systems: RENAL, PADUA, SPARE, DAP, ABC, C-index, NePhRO, Renal Pelvic Score and Zhongshan. Receiver operating characteristic (ROC) curve analyses were performed to assess the diagnostic performance of each scoring system for predicting malignant histology. Associations between nephrometry scores and malignant histology were evaluated using univariable and multivariable logistic regression analyses. Benign pathology was observed in 30.6% of patients. In univariable analyses, PADUA ( p = 0.003), RENAL ( p = 0.002), SPARE ( p = 0.010), DAP ( p = 0.012), ABC ( p = 0.011), and Zhongshan ( p = 0.044) scores were significantly associated with malignant histology. The C-index demonstrated the highest diagnostic performance (AUC = 0.850, p < 0.001). In multivariable analysis, the C-index remained the only independent predictor of malignancy (OR = 0.490, 95% CI 0.246–0.974, p = 0.042). Higher C-index values were associated with benign tumors, whereas lower values were associated with clear-cell renal cell carcinoma. Anatomical nephrometry scores, particularly the C-index, may serve as practical preoperative indicators of tumor biology in SRMs. Incorporating the C-index into clinical evaluation may improve risk stratification and potentially help reduce unnecessary surgical treatment for benign lesions after further validation.