Fine-needle aspiration of renal cell carcinoma: is accurate Fuhrman grading possible on cytologic material?

The Fuhrman grading system of renal cell carcinoma (RCC) consists of four grades based on nuclear size/contour and nucleolar conspicuousness. Fuhrman grading of histpathologic material is an independent prognostic parameter for RCC. Although widely used in surgical pathology, Fuhrman grading is not routinely performed on cytologic material. Thirty-three cases of renal fine needle aspirations (FNAs) with histologically proven RCC were retrieved from the cytopathology archives at Johns Hopkins Hospital. Fuhrman grade was determined independently and blindly by three faculty cytopathologists and compared with the Fuhrman grade of the subsequent surgical pathology specimen. The 33 resection specimens had the following Fuhrman grades: 0/33, grade I; 24/33 (73%), grade II; 9/33 (27%), grade III; and 0/33, grade IV. After Fuhrman grading was applied to the FNA material, diagnostic sensitivity was 83% for grade II versus 44% for grade III. The specificity and accuracy were 50 and 75%, respectively, for grade II versus 100% and 84% for grade III. Diagnostic sensitivity for grade II tumors ranged from 38 to 83%, grade III 44-62%. Diagnostic specificity for grade II tumors ranged from 50 to 78%, grade III 80-100%. Accuracy ranged from 48 to 75% for grade II and 75-87% for grade III. Using a two-tier grading model, accuracy improved to 84.2%. In our experience, Fuhrman grading of FNA specimens yielded variable results. There was only moderate agreement between cytopathologists, with an overall tendency to undergrade the tumor when compared with the resection specimen. Averaging the participants' grading and using a two-tier instead of four-tier system improved overall performance.
(Copyright © 2010 Wiley-Liss, Inc.)