This study aims to identify CT features that potentially differentiate renal Oncocytomas, Lipid poor angiomyolipoma (LPAML), Papillary renal cell carcinoma (PRCC) and Chromophobe renal cell carcinoma (ChRCC).

Twenty eight patients with histologically proven renal oncocytomas (6), LPAML (8), PRCC (8) and ChRCC(6) were included. All patients underwent 128-slice CT examinations with plain and three contrast-enhanced phases. Imaging findings of these patients were retrospectively analyzed by 2 board certified radiologists. Lesion homogeneity, presence/absence of tumor necrosis, central scars, tumor vessels and enhancement kinetics were evaluated. The differences of CT values of the tumours between three contrast-enhanced phases and plain scan were calculated and recorded; differences of tumor CT values between corticomedullary phase and...

Tumor appearances were highly variable with intra-tumoural heterogeneity seen in Oncocytomas (6/6) (Fig. 1), LPAML (2/8) (Fig. 2), PRCC (6/8) (Fig. 3) and ChRCC (2/6) (Fig. 4). Tumor necrosis was more common in PRCC (6/8) compared to ChRCC (2/6), Oncocytoma (2/6) and LPAML (1/8). Central scars were only present in Oncocytomas (6/6) and none of the other three tumors. Abnormal vascularity and intra-tumoural vessels could be seen in malignant tumours (PRCC and ChRCC) (7/14) (Fig. 4); malformed vessels could be seen in LPAML (5/8) (Fig....

A combination of CT imaging features and enhancement kinetics were useful in distinguishing these 4 types of solid renal tumours. Benign tumours were more likely to have rapid enhancement and slow washout compared to malignant tumours where more gradual increase in enhancement was seen. Tumour necrosis was more often encountered in PRCC. Central scars in oncocytomas and malformed vessels in LPAML may be relatively common in comparison with other tumours.

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