Percutaneous renal mass biopsies with no viable lesional cells - Recognizing different histologic patterns can help...

Percutaneous renal mass biopsy (RMB) is increasingly used for diagnosis and management of renal masses. Nondiagnostic RMBs are not uncommon, with large series reporting nondiagnostic RMB rates to be 10%-21%, and they can trigger challenging clinical scenarios and confusions for clinicians. 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. 539 consecutive RMBs performed between 2005 and 2024 were retrospectively identified in this study. Out of the 539 cases, sixty-four (12%) were nondiagnostic, defined as no viable tumor cells. Six of the sixty-four cases were excluded (5 cases being repeat biopsies of the previous nondiagnostic biopsies; 1 case lost to follow up). Histological patterns were categorized, and clinical outcomes were assessed via electronic medical records. Upon review, seven histological patterns were identified. Patterns 1-4 (benign parenchyma, chronic changes, tumor necrosis, hyalinized stroma) were associated with malignancy in 31/42 cases (74%). Patterns 5-7 (xanthogranulomatous pyelonephritis, crescentic glomerulonephritis, blood clots/macrophages/fibrosis/amorphous material) were associated with malignancy in only 2/16 cases (12.5%). There was a statistically significant difference by chi-square test (p < 0.000005) between Patterns 1-4 and Patterns 5-7. In summary, certain histological features in nondiagnostic RMBs can help predict nondiagnostic vs. true negative biopsy and guide subsequent clinical decision-making. Recognition of these histologic patterns could aid pathologists in appropriately classifying nondiagnostic vs. true negative RMBs, improving patient management, and potentially reducing the risk of missed malignancy.