Accuracy of Fine Needle Aspiration in Distinguishing Subtypes of Renal Cell Carcinoma

OBJECTIVE: To evaluate the cytologic features of each subtype of renal cell carcinoma (RCC) for separating the various subtypes. STUDY DESIGN: Thirty-eight renal fine needle aspiration (FNA) specimens with surgical resection follow-up were retrospectively reviewed and classified without knowledge of the resection specimen diagnosis. These included 18 clear cell RCCs, 8 papillary RCCs, 4 oncocytomas, 2 chromophobe RCCs, 2 sarcomatoid RCCs and 4 metastases to the kidney. RESULTS: Seventy-four percent of the primary renal lesions were correctly classified. All 4 oncocytomas and the 2 chromophobe tumors were correctly classified, while both sarcomatoid RCCs and 3 of 8 papillary RCCs were misclassified as clear cell RCC. One clear cell RCC was misclassified as papillary type. Two clear cell and one papillary RCC were nondiagnostic; in each case the tumor had a prominent cystic component. All four metastases were correctly identified. CONCLUSION: Subclassification of RCC by FNA is relatively accurate. In this study, the most common error was to misclassify papillary and sarcomatoid RCC as clear cell RCC.