Touch Preparation for Rapid On-Site Evaluations of Renal Mass Biopsies: Concordance Rate, Pearls and Pitfalls

Abstract Introduction Core needle biopsy (CNB) of renal masses has not been commonly performed due to the perceived low sensitivity until recent years. Rapid on-site evaluation (ROSE) using touch preparations (TPs) has the potential to improve the yield of CNB, however, it can be challenging due to the diverse morphology of various types of renal tumors and native cells. Materials and Methods We retrospectively reviewed percutaneous CNBs of renal masses with ROSE using TPs. ROSE findings were correlated with diagnoses on CNBs. Results Among the 165 cases identified between August 2016 and August 2019, CNB led to definitive diagnoses in 82.4% (136/165) 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 a case of lymphoma (0.6%). Eight cases were indeterminate including two cases positive for oncocytic neoplasm, two cases suspicious for RCC, and four 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 (NOS) (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%. Conclusions Renal mass CNBs revealed a significant number 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 identify low grade RCCs.