Commentary on “Predicting the histology of small renal masses using preoperative dynamic contrast-enhanced magnetic resonance imaging.” Kim JH, BaeJH, Lee KW, Kim ME, Park SJ, Park JY, Department of Urology, Soonchunhyang University Hospital, Seoul, Korea

To study if the magnetic resonance imaging can predict the histologic type of small renal cell carcinoma. c contrast-enhanced magnetic resonance imaging was performed on 63 patients with computed tomography-suspected or ultrasonography-suspected small (≤4 cm) renal cell carcinoma from February 2008 to February 2010. Percentage signal intensity change, tumor-to-cortex enhancement index during precontrast phase, corticomedullary phase, and nephrogenic phase were investigated. the 60 patients, 42 were proven to have clear cell renal cell carcinoma and 18 patients were proven to have nonclear cell renal cell carcinoma (10 patients with papillary renal cell carcinoma and 8 patients with chromophoberenal cell carcinoma). The percentage signal intensity change in the clear cell-type was higher only in the corticomedullary phase (P = 0.002). The tumor-to-cortex enhancement index in the clear cell type was higher in the corticomedullary and nephrogenic phases (P = 0.007 and P = 0.041, respectively). The most valuable marker was percentage signal intensity change in the corticomedullary phase (area under the receiver operating characteristic curve 0.85). The cutoff value of percentage signal intensity change in the corticomedullary phase was 173%, and the sensitivity and specificity were 81% and 87.5%, respectively. c contrast-enhanced magnetic resonance imaging could be useful for discriminating the clear cell type from nonclear cell type in small renal cell carcinoma with high sensitivity and specificity.