Percutaneous core needle biopsy for renal mass is increasingly utilized to provide histological diagnoses, helping to avoid unnecessary surgery for indolent lesions, guide decisions for surveillance, and obtain tissue samples before ablative or systemic treatments [1], [2], [3]. When abdominal imaging studies provide high diagnostic accuracy, and a needle biopsy is not always necessary before surgery, especially in patients whose imaging studies are consistent with RCC [1], [2], [3]. While the details of the indication for the renal mass biopsies (RMBs) vary slightly between major guidelines, the general theme is that RMBs should be considered when it is clinicoradiologically uncertain when a renal mass is whether of renal cell origin (i.e. rule out urothelial carcinoma, metastasis, infectious, hematopoietic malignancy, etc.), except in cases when it is unlikely to change clinical management regardless of the pathological diagnosis [1], [2], [3]. Additionally, needle biopsy could also be considered to establish the diagnosis of RCC vs. benign renal neoplasm such as oncocytoma, which may help guide decision-making on active surveillance strategies, particularly in the elderly patients with poor living status [1], [2], [3].

Ultrasound-guided percutaneous core needle biopsy is currently the gold standard for the RMBs. A meta-analysis by Marconi et al. including 57 studies and 5228 patients demonstrated an overall median diagnostic rate of 92%, with sensitivity and specificity of 99.1% and 99.7%, respectively [4]. While the sensitivity and the specificity are nearly 100%, nondiagnostic biopsies constitute a non-negligible proportion of RMBs, which could lead to clinical uncertainty, delayed management, and patient anxiety. Large series have reported nondiagnostic rates of 10%–21% [5], [6], [7], [8], [9], [10], [11]. Some of the nondiagnostic results are attributable to technical limitations—such as suboptimal technique, needle type, or imaging guidance—or intrinsic procedural challenges, including respiratory motion [5], [6], [7]. Beyond the technical limitations, some studies have shown that the factors that could influence the nondiagnostic yield include the lesion size, cystic versus solid composition, enhancement characteristics, and skin-to-tumor distance [5], [6], [8].

Per Leveridge et al., nondiagnostic biopsy results should not be treated as a negative result and a repeat biopsy should be considered, as many patients in this category are later shown to have renal malignancy [8]. However, it can be challenging for both clinicians and pathologists regarding how one can determine whether a biopsy without lesional cells is truly negative vs. nondiagnostic. Therefore, this study aims to evaluate whether specific histologic patterns seen in RMBs without lesional cells are associated with clinical outcomes and whether such findings could help guide the management in this clinical scenario.