Touch preparation for rapid onsite evaluations of renal mass biopsies: concordance rate, pearls, and pitfalls

Core needle biopsy (CNB) of renal masses has not been commonly performed because of the perceived low sensitivity until recent years. Rapid onsite evaluation (ROSE) using touch preparations (TPs) has the potential to improve the yield of CNB, although it can be challenging because of the diverse morphology of various types of renal tumors and native cells.

We retrospectively reviewed percutaneous CNBs of renal masses with ROSE using TPs. ROSE findings were correlated with diagnoses on CNBs.

Among the 165 cases identified between August 2016 and August 2019, CNB led to definitive diagnoses in 82.4% (136 of 165) cases. These included renal cell carcinomas (RCCs) (n = 113, 68.5%), benign neoplasms (n = 14, 8.5%), urothelial carcinomas (n = 6, 3.6%), metastatic carcinomas (n = 2, 1.2%) and 1 case of lymphoma (0.6%). Eight cases were indeterminate, including 2 cases positive for oncocytic neoplasm, 2 cases suspicious for RCC, and 4 cases with atypical features. Twenty-one (12.7%) CNBs were negative for tumor. ROSE interpretations for these cases were: malignant (n = 18, 10.8%); positive for neoplasm (n = 6, 3.6%); atypical/lesional/adequate not otherwise specified (n = 113, 68.5%); negative (n = 19, 11.5.0%); and unsatisfactory (n = 9, 5.5%). The overall concordance rate between ROSE and the final CNB diagnoses was 87.3%.

Renal mass CNBs revealed a subset of non-surgical conditions in addition to RCCs. ROSE using TPs showed a high concordance rate with CNB results. Proximal tubular cells, macrophages, and angiomyolipomas are common pitfalls, whereas vacuolated cytoplasm and background are helpful features to confirm low-grade RCCs.