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 both T1‐ and T2‐weighted images were classified into hypointensity, isointensity, and hyperintensity. Each tumor was pathologically classified into four types: alveolar, papillary, tubular, and cystic. These findings were correlated with MR signal intensities. Alveolar tumors showed hypointensity to isointensity on T1‐weighted image and isointensity to hyperintensity on T2‐weighted image. In contrast, all papillary tumors showed hypointensity on T2‐weighted image. Four of six tumors with hypointensity on T2‐weighted image were caused by hemosiderin deposition, hemorrhage, and necrosis. However, there were two papillary RCCs that showed hypointensity on T2‐weighted image despite no hemosiderin deposition and no hemorrhage. We conclude that papillary RCC is associated with T2‐hypointense appearance as well as hemosiderin deposition, hemorrhage, and necrosis.