Differentiation of Subtypes of Renal Cell Carcinoma on Helical CT Scans

The purpose of our study was to differentiate subtypes of renal cell carcinoma on helical CT scans. We reviewed CT scans of four subtypes of renal cell carcinoma: 76 conventional (clear cell), 19 papillary, 13 chromophobe, and two collecting duct. Biphasic CT scans (unenhanced, corticomedullary, and excretory phase scans) were obtained in 61 patients, and monophasic CT scans (unenhanced and excretory phase scans) in 49. We compared patient age and sex; tumor size; degree and pattern (homogeneous, heterogeneous, predominantly peripheral) of enhancement; presence or absence of calcification; and tumor-spreading patterns including perinephric change, venous invasion, and lymphadenopathy in four subtypes. Conventional renal carcinoma showed stronger enhancement than the other subtypes (p < 0.05): 106 +/- 48 H (mean +/- SD) in the corticomedullary phase and 62 +/- 25 H in the excretory phase. The sensitivity and specificity for differentiating conventional renal carcinoma from the other subtypes were 74% and 100% when 84 H was used as the cutoff value in the corticomedullary phase and 84% and 91% when 44 H was used as the cutoff value in the excretory phase. Conventional (84%), papillary (74%), and collecting duct (100%) renal carcinomas tended to show heterogeneous or predominantly peripheral enhancement, whereas chromophobe renal carcinoma (69%) usually showed homogeneous enhancement. Calcification was more common in papillary (32%) and chromophobe (38%) renal carcinomas than in conventional renal carcinoma (11%) (p < 0.05). Perinephric change and venous invasion were not noted in chromophobe renal carcinoma, whereas both were common in collecting duct renal carcinoma. For the differentiation of the subtypes of renal cell carcinoma, degree of enhancement is the most valuable parameter; enhancement pattern, the presence or absence of calcification, and tumor-spreading patterns can serve supplemental roles in the identification of the subtype of renal cell carcinoma.