Clear Cell Renal Cell Carcinoma: Discrimination from Other Renal Cell Carcinoma Subtypes and Oncocytoma at Multiphasic Multidetector CT

To determine whether enhancement at multiphasic multidetector computed tomography (CT) can help differentiate clear cell renal cell carcinoma (RCC) from oncocytoma, papillary RCC, and chromophobe RCC.With institutional review board approval for this HIPAA-compliant retrospective study, the pathology database was queried to derive a cohort of 298 cases of RCC and oncocytoma with preoperative multiphasic multidetector CT with as many as four phases (unenhanced, corticomedullary, nephrographic, and excretory). A total of 170 clear cell RCCs, 57 papillary RCCs, 49 oncocytomas, and 22 chromophobe RCCs were evaluated for multiphasic enhancement and compared by using t tests. Cutoff analysis was performed to determine optimal threshold levels to discriminate among the four groups.Mean enhancement of clear cell RCCs and oncocytomas peaked in the corticomedullary phase; mean enhancement of papillary and chromophobe RCCs peaked in the nephrographic phase. Enhancement of clear cell RCCs was greater than that of oncocytomas in the corticomedullary (125 HU vs 106 HU, P = .045) and excretory (80 HU vs 67 HU, P = .034) phases. Enhancement of clear cell RCCs was greater than that of papillary RCCs in the corticomedullary (125 HU vs 54 HU, P < .001), nephrographic (103 HU vs 64 HU, P < .001), and excretory (80 HU vs 54 HU, P < .001) phases. Enhancement of clear cell RCCs was greater than that of chromophobe RCCs in the corticomedullary (125 HU vs 74 HU, P < .001) and excretory (80 HU vs 60 HU, P = .008) phases. Thresholding of enhancement helped to discriminate clear cell RCC from oncocytoma, papillary RCC, and chromophobe RCC with accuracies of 77% (83 of 108 cases), 85% (101 of 119 cases), and 84% (81 of 97 cases).Enhancement at multiphasic multidetector CT, if prospectively validated, may assist in the discrimination of clear cell RCC from oncocytoma, papillary RCC, and chromophobe RCC.