Multiparametric magnetic resonance imaging for the differentiation of low and high grade clear cell renal carcinoma

Purpose To retrospectively evaluate the ability of magnetic resonance (MR) imaging to differentiate low from high Fuhrman grade renal cell carcinoma (RCC). Materials and methods MR images from 80 consecutive pathologically proven RCC (57 clear cell, 16 papillary and 7 chromophobe) were evaluated. Double-echo chemical shift, dynamic contrast-enhanced T1- and T2-weighted images and apparent diffusion coefficient (ADC) maps were reviewed independently. Signal intensity index (SII), tumour-to-spleen SI ratio (TSR), ADC ratio, wash-in (WiI) and wash-out indices (WoI) between different phases were calculated and compared to pathological grade and size. The Fuhrman scoring system was used. Low grade (score <= 2) and high grade (score <= 3) tumours were compared using univariate and multivariate analyses. Results No associations between grade and imaging factors were found for papillary and chromophobe RCCs. For clear cell RCCs, there was a significant association between the grade and parenchymal WiI (WiI2) (P=0.02) or ADCr (P=0.03). A significant association between tumour grade and size (P=0.01), WiI2 (P=0.02) and ADCr (P=0.05) remained in multivariate analysis. Conclusions Multiparametric MRI can be used to accurately differentiate low Fuhrman grade clear cell RCC from high grade. High Fuhrman grade (>= 3) RCCs were larger, had lower parenchymal wash-in indices and lower ADC ratios than low grade.