Role of diffusion-weighted magnetic resonance imaging and apparent diffusion coefficient in subtyping renal cell...

Diffusion-weighted magnetic resonance imaging (DWI) has emerged as a non-contrast functional imaging technique for renal mass characterization. Its role in differentiating histopathological subtypes of renal cell carcinoma (RCC) remains an area of active investigation.

To evaluate the role of DWI and apparent diffusion coefficient (ADC) values in differentiating histopathological subtypes of RCC.

In this prospective observational study, 127 patients with histopathologically proven RCC who underwent preoperative magnetic resonance imaging (MRI) including DWI were analyzed. Diffusion-weighted imaging was performed using b values of 0 second/mm² and 1000 seconds/mm², and ADC maps were generated. ADC values were measured from solid tumor components and compared among RCC subtypes. Statistical analysis included subgroup comparisons and receiver operating characteristic curve analysis to assess the ability of ADC values to differentiate clear cell RCC (ccRCC) from non-ccRCC.

Of the 127 RCCs, 97 (76.4%) were ccRCC, 24 (18.9%) papillary RCC, and 6 (4.7%) chromophobe RCC. The mean ADC value of ccRCC [(1.391 ± 0.271) × 10^-3 mm²/second] was significantly higher than that of papillary RCC [(0.876 ± 0.293) × 10^-3 mm²/second; P < 0.001] and chromophobe RCC [(1.059 ± 0.369) × 10^-3 mm²/second; P = 0.04]. No significant difference was observed between papillary and chromophobe RCC (P = 0.396). When grouped, ccRCC demonstrated a significantly higher mean ADC value compared with non-ccRCC [(1.391 ± 0.271) × 10^-3 mm²/second vs (0.915 ± 0.312) × 10^-3 mm²/second; P < 0.001]. Receiver operating characteristic analysis yielded an area under the curve of 0.889 (95% confidence interval: 0.804-0.975). An ADC threshold of 1.08 × 10^-3 mm²/second achieved 90% sensitivity and 83% specificity for identifying ccRCC.

DWI with quantitative ADC analysis reliably differentiates clear cell from non-ccRCC and demonstrates significant correlation with RCC subtype and tumor grade. DWI serves as a valuable adjunct to conventional MRI, particularly in patients with contraindications to contrast administration.