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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.
Renshaw et al. (Wed,) studied this question.