Diffusion-weighted imaging versus contrast-enhanced MR imaging for the differentiation of renal oncocytomas and chromophobe renal cell carcinomas.

OBJECTIVES

To compare the performance of diffusion-weighted imaging (DWI) with that of contrast-enhanced MRI in differentiating renal oncocytomas from chromophobe renal cell carcinomas (RCCs).

METHODS

We recruited 48 patients with histopathologically confirmed renal oncocytomas (n=16) and chromophobe RCCs (n=32). All patients underwent preoperative DWI and contrast-enhanced MRI. Apparent diffusion coefficient (ADC) and signal intensity were measured in each patient. ADC ratio and percentage of signal intensity change were calculated.

RESULTS

Mean ADC values for renal oncoctytomas were significantly higher than those for chromophobe RCCs (1.59±0.21 vs. 1.09±0.29× 10 mm/s, p < 0.001). Area under the ROC curve, sensitivity and specificity were 0.931, 87.5% and 84.4%, respectively, for ADC measurement of DW imaging; 0.825, 87.5% and 75%, respectively, for enhancement ratio (p > 0.05). Adding ADC values to the enhancement ratios in the ROC, analysis to differentiate renal oncocytoma from chromophobe RCCs increased specificity from 75 to 87.5% at 87.5% sensitivity without significantly increasing the AUC (0.930).

CONCLUSIONS

Both DWI and contrast-enhanced MRI may assist in differentiating renal oncocytomas from chromophobe RCCs, with DWI showing higher diagnostic value. The combination of the two parameters could potentially provide better performance in distinguishing these two tumours.

KEY POINTS

• ADC values can assist in differentiating renal oncocytomas from chromophobe RCCs. • DW imaging possesses better specificity than does contrast-enhanced MR imaging. • Combining the two parameters provides higher specificity regarding the differential diagnosis.