Objectives: Complex cystic renal lesions pose a significant diagnostic challenge in the preoperative assessment of malignancy. Although percutaneous renal mass biopsy is well established for solid tumours diagnosis, its role in cystic lesions remains controversial. This systematic review aims to evaluate the diagnostic performance, safety, and clinical impact of percutaneous sampling—fine-needle aspiration (FNA) and core needle biopsy (CNB)—in Bosniak III–IV renal cysts. Methods: A systematic review and meta-analysis were conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines International Prospective Register of Systematic Reviews (PROSPERO) ID CRD420251124563. PubMed/MEDLINE (Medical Literature Analysis and Retrieval System Online), Embase, Cochrane Central Register of Controlled Trials (CENTRAL), Scopus, and Web of Science were searched (1980–May 2025). Eligible studies included adult patients with Bosniak III–IV cysts undergoing FNA or CNB. Pooled diagnostic estimates were calculated using a bivariate random-effects model. Results: Seven studies, including 954 patients, met the inclusion criteria. Three studies evaluated FNA, yielding a pooled sensitivity of 59% 95% Confidence Interval (CI): 14–93, specificity of 84% (95% CI: 62–94), and an overall diagnostic performance of 0.84 Area under the curve (AUC). Sensitivity estimates varied widely, whereas specificity was consistently high. Four studies assessed CNB, reporting diagnostic yields between 75% and 81%. Cystic morphology was identified as the strongest independent predictor of non-diagnostic sampling, with odds ratios (OR) up to 13.9. No major complications or cases of tumour seeding were reported across the included studies. Reporting of minor complications was limited and heterogeneous, precluding a pooled analysis. Conclusions: Percutaneous sampling of Bosniak III–IV cystic renal masses is feasible but diagnostically challenging. FNA provides limited value due to high rates of non-diagnostic and false-negative results. CNB achieves higher accuracy, particularly when a solid component is present, and may be considered within a multidisciplinary setting when histological confirmation is likely to influence treatment decisions.
Barretta et al. (Thu,) studied this question.