Objective: To compare and analyze the MRI features of different renal cell carcinoma (RCC) subtypes.
Methods: The MR images of 81 surgically and pathologically confirmed renal cell carcinomas from 79 patients were reviewed retrospectively. The MR imaging features of lesions in plain scan, the degree and patterns of lesion enhancement (homogeneous, heterogeneous, peripheral), and tumor spreading patterns were analyzed. In order to evaluate the diagnostic validity of differentiating RCC subtypes using signal enhancement, receiver operating characteristic curves (ROC) were generated. The cutoff value of post-contrast signal intensity to noise ratios (SNR) of the tumor parenchyma were also generated in order to differentiate clear cell RCC from other subtypes.
Results: Of the 81 lesions, 58 were clear cell carcinomas, 10 chromophobe cell carcinomas, 8 papillary cell carcinomas, and 5 unclassified RCC. All the chromophobe cell subtype tumors showed a homogeneous density (P < 0.05). The clear cell subtype tumors were likely heterogenous, and also showed heterogenous enhancement with mixed signal than other subtypes (P < 0.05). The cutoff value of SNR, which was used to differentiate clear cell subtype from the other subtypes, were 616 (corticomedullary phase), 579 (nephrographic phase) and 278 (excretory phase), retrospectively. The nephrographic phase is the most appropriate for differentiation, with a sensitivity of 62.1%, specificity of 91.3%, positive predictive value of 94.7%, negative predictive value of 48.8% and an accuracy value of 70.3%. No significant difference was found in tumor spreading patterns among all subtypes of RCC.
Conclusion: MR imaging features, particularly tumor heterogeneity and degree of enhancement are useful in differentiation of the renal cell carcinoma subtypes, and in choosing an individualized therapy.