MRI Features of Renal Cell Carcinoma That Predict Favorable Clinicopathologic Outcomes

OBJECTIVE. The purpose of this article is to determine whether MRI features of renal cell carcinoma (RCC), such as enhancing solid component and T1 signal intensity, are associated with clinicopathologic outcomes. MATERIALS AND METHODS. This retrospective study included 241 RCCs in 230 patients who underwent preoperative MRI, had pathologic analysis results available, and were monitored for at least 3 months. A radiologist assessed tumor features on MRI, including unenhanced T1 signal relative to renal cortex and the percentage of solid enhancing components. The electronic medical record or follow-up images were reviewed to assess for the development of local recurrence or metastases. Statistical analysis was performed to correlate imaging features at MRI with pathologic and clinical outcome. RESULTS. The following tumor features were observed: predominantly cystic morphologic features (defined as solid component <= 25%, n = 33), solid component greater than 25% (n = 208), T1 hypointensity (n = 97), and T1 intermediate intensity or hyperintensity (n = 144). Local recurrence or metastases were observed in 14 patients. Compared with T1-in-termediate or -hyperintense lesions, T1-hypointense RCCs were more likely to be low stage (90.7% vs 74.3%; p = 0.001) and low grade (78.9% vs 41.8%; p < 0.001) and had a lower rate of recurrence or metastases (3.3% vs 8%; p = 0.167). Compared with lesions with greater than 25% solid enhancement, predominantly cystic RCCs were more likely to be lower stage (93.9% vs 78.8%; p = 0.053) and lower grade (94.7 vs 56.5%; p < 0.001) and to have no incidence of recurrence or metastasis (0% vs 6.9%; p = 0.227). RCCs that were both cystic and T1 hypointense (n = 14) were lower stage (100% vs 79.6%; p = 0.047) and lower grade (92.9% vs 58.1%; p = 0.01) and had no recurrence or metastases on follow-up. CONCLUSION. Cystic and T1-hypointense RCC show less-aggressive pathologic features and favorable clinical behavior.