OBJECTIVETo investigate the role of multiphasic spiral computed tomography (SCT) in the differential diagnosis of small renal cell carcinoma.

METHODSThe data of 100 patients with small renal cell carcinoma (< or = 3.0 cm) proved by pathology were retrospectively reviewed in order to analyze the features of SCT during plain, corticomedullary and excretory phases. There were 83 males and 17 females, with a mean age of 54. 3 years ranging from 9 to 81 years.

RESULTSThere were 38 tumor masses in the left kidney and 62 in the right one. They were 1.0-3.0 cm (mean, 2.5 cm) in the greatest dimension. According to the 2004 WHO histological classification criteria for the tumors of the kidney. Seventy-six patients had clear cell renal cell carcinoma, 4 multilocular clear cell renal cell carcinomas, 9 papillary renal cell carcinoma, 4 chromophobe renal cell carcinomas and 7 unclassified renal cell carcinomas. Clear cell renal cell carcinoma exhibited rich blood supply and inhomogeneous density due to hemorrhage, necrosis or cystic degeneration. Multilocular clear cell renal cell carcinoma presented as a multilocular cystic mass with thin wall and septa, instead of an expansile nodule. Papillary renal cell carcinoma showed inhomogeneous density and hypovascular distribution. Chromophobe renal cell carcinoma was relatively homogeneous and hypovascular. Compared with clear cell renal cell carcinoma, unclassified renal cell carcinoma showed inhomogeneous density and hypervascular distribution with more invading growth features than the other subtypes.

CONCLUSIONCommonly encountered subtypes of the small renal cell carcinoma exhibit their own specific features in multiphasic spiral CT, which may be helpful in differential diagnosis, but each subtype should be differentiated from the renal oncocytoma, cystic nephroma, complex renal cyst, renal angiomyolipoma with minimal fat and renal infiltrating urothelial carcinoma.