Biopsy Provides Actionable Information Associated with Treatment Decisions for 2-7 cm Renal Masses.

Background/Objectives: Renal mass biopsy (biopsy) is increasingly incorporated into the evaluation of localized renal masses, yet its role in guiding management remains variable among clinical practices. We evaluated the clinical association of biopsy using a simplified classification system categorizing biopsy results as Biopsy Actionable for Immediate Treatment (BAIT) or Biopsy Actionable for Active Surveillance (BAAS)-assessing how biopsy-derived histology influences real-world management. Methods: We identified all patients undergoing biopsy for a renal mass measuring 2-7 cm at a single academic center between 2010 and 2025. After excluding nondiagnostic biopsies, repeat biopsies, and biopsies performed for metastatic diagnosis, 1395 patients formed the analytic cohort. Histologic subtypes and initial treatment were evaluated. Multivariable logistic regression assessed predictors of (1) radical versus partial nephrectomy, (2) surgery versus thermal ablation, and (3) active surveillance versus intervention, adjusting for tumor diameter, age, and BAIT/BAAS status. Results: Of 1395 patients, 1119 (80.2%) had BAIT pathology and 276 (19.8%) had BAAS pathology. Initial management included surgery (36.3%), thermal ablation (36.3%), active surveillance (24.2%), no treatment (1.7%), and radiation (1.5%). BAAS pathology was strongly associated with the selection of active surveillance (OR 21.80, p < 0.001). Larger tumor diameter was the principal driver of radical nephrectomy (OR 2.04/cm, p < 0.001) and of choosing surgery over ablation (OR 2.05/cm, p < 0.001). Younger age was associated with selection of surgery over ablation (OR 0.93/year, p < 0.001). Biopsy histology showed a stronger association with surveillance selection than either tumor diameter or age. Conclusions: Biopsy provides actionable diagnostic information for patients with 2-7 cm renal masses, identifying benign or indolent pathology in nearly one in five patients. BAIT/BAAS categorization was strongly associated with the selection of active surveillance for renal masses.