Differential radiologic characteristics of renal tumours on multiphasic computed tomography

This study analysed the tumour attenuation characteristics of different subtypes of renal cell carcinomas (RCCs), including clear cell RCC (ccRCC), papillary RCC (pRCC), mixed RCC, chromophobe RCC (chRCC) and oncocytoma.

We randomly selected 100 RCC cases that underwent nephrectomy between 2004 and 2012 from a collaborative database. Of these cases, 36 were excluded due to the absence of available imaging. The remaining 64 cases comprised 35 ccRCCs, 11 pRCCs, eight chRCCs, seven mixed RCCs and three oncocytomas. The cases were classified as computed tomography (CT) kidney, CT urogram (with plain, nephrographic and pyelographic phases) or CT abdomen (with portovenous and delayed phases). A circular region of interest (ROI) ≥ 1 cm² was drawn and the same standard ROI size was used for each phase at the same site; three different circular ROIs were drawn per lesion per phase. Analysis of variance and t-test were used to examine differences in the radiological characteristics.

There was no statistical difference in the attenuation and degree of enhancement between mixed RCCs and ccRCCs. The attenuation and degree of enhancement of the oncocytomas were significantly higher than those of the other RCC subtypes.

While mixed RCCs did not have attenuation characteristics that differed significantly from those of ccRCCs, oncocytomas can be distinguished from ccRCCs, pRCCs, chRCCs and mixed RCCs by their high radiological density and enhancement. The ability to differentiate oncocytomas from these tumours potentially allows the preoperative selection of patients with small renal masses for conservative management.