Risk of malignancy of cytologic categories and post-biopsy clinical management of renal oncocytic neoplasms

Renal mass biopsy (RMB) cytology is increasingly used for the pretreatment evaluation of renal masses. Cytopathologic classification of RMB specimens facilitates communication with clinicians and provides valuable risk stratification to guide management decisions. This study evaluated the risk of malignancy (ROM) associated with RMB cytology in renal oncocytic neoplasms (ONs).

The renal neoplasms with oncocytic features were reclassified per the 5th edition of the WHO Classification of Tumors. RMB cases were assigned to six diagnostic categories: 1) nondiagnostic (ND), 2) benign, 3) low risk oncocytic neoplasm (LRON), 4) atypical, 5) suspicious for malignancy (SFM), and 6) malignant.

In total, 198 RMB cases with oncocytic features were identified, comprising oncocytoma (111 [56%]), chromophobe renal cell carcinoma (RCC) (55 [28%]), LRON (10 [5%]), hybrid oncocytic neoplasm (8 [4%]), low-grade oncocytic tumor (7 [4%]), papillary RCC (6 [3%]), and eosinophilic vacuolated tumor (1 [1%]). The overall ROM for ONs was 35%. ROMs by category were ND (29%), benign (2%), LRON (30%), atypical (100%), SFM (50%), and malignant (100%). Post-RMB resection was more frequently used for malignant (36 of 57 [63%]), SFM (1 of 2 [50%]), and ND (4 of 7 [57%]), whereas active surveillance was more frequently employed for benign ON (100 of 111 [90%]) and LRON (12 of 20 [60%]). Cryoablation was used in 9% (18 of 198) of ONs.

This study defines ROMs across cytologic categories of ONs to stratify the risks and underscores the valuable role of RMB. These findings provide a framework for clinicians to make informed decisions based on cytologic classification and associated ROM.