Small renal cell carcinoma: MRI with pathologic correlation

The MRI features of small renal cell carcinomas (RCCs) were retrospectively reviewed and correlated with histology in 24 patients. MRI features on bot h T1- and T2-weighted images were classified into hypointensity, isointensi ty, and hyperintensity. Each tumor was pathologically classified into four types: alveolar, papillary, tubular, and cystic. These findings were correl ated with MR signal intensities. Alveolar tumors showed hypointensity to is ointensity on T1-weighted image and isointensity to hyperintensity on T2-we ighted image. In contrast, all papillary tumors showed hypointensity on TP- weighted image. Four of six tumors with hypointensity on T2-weighted image were caused by hemosiderin deposition, hemorrhage, and necrosis. However, t here were two papillary RCCs that showed hypointensity on Ta-weighted image despite no hemosiderin deposition and no hemorrhage. We conclude that papi llary RCC is associated with T2-hypointense appearance as well as hemosider in deposition, hemorrhage, and necrosis.