Differentiation between renal oncocytomas and chromophobe renal cell carcinomas using dynamic contrast-enhanced computed tomography.

PURPOSE To evaluate the ability of inferior vena cava-lesion-attenuation-difference (ILAD) and lesion-cortex-attenuation-ratio (LCAR) to differentiate renal oncocytomas (RO) from chromophobe renal cell carcinomas (chRCC). METHODS Retrospective study with analysis of 84 cases of chRCC and 30 cases of RO confirmed by surgical pathology. ILAD was calculated by measuring the difference in Hounsfield units (HU) between the inferior vena cava and the lesion of interest on the same image slice on preoperative CT scan. Calculating LCAR using the CT attenuation ratio of lesion to renal cortex at the same image slice. Receiver operating characteristic (ROC) curves were plotted to analyze the diagnostic values of ILAD and LCAR for disease activity. RESULTS There were no statistically significant differences in demographic and lesion characteristics between patients with chRCC and RO (p > 0.05). ILAD has significant statistical differences in the identification of RO and chRCC in the arterial (p = 0.031), venous (p = 0.047), and delayed phase (p = 0.002). And LCAR showed a statistically significant difference between two lesions during the arterial (p = 0.043), venous (p = 0.026), and delayed phase (p = 0.008). When all significant variables were used in combination to build a predicting model (Mix), the AUC was 0.871 (95% CI 0.759-0.984) with 67.9% sensitivity and 100% specificity. CONCLUSION ILAD and LCAR at the arterial phase, venous phase and delayed phase were shown to be useful CT attenuation parameter in discriminating RO from chRCC when histologic evaluation on biopsy is indeterminate.