Correlation between pathology and MR tomography and differential diagnosis of malignant kidney tumors.

Purpose: Evaluation of malignancy criteria in MRT of kidney tumors in correlation with the histopathological findings. Materials and Methods: 41 patients with suspected malignant kidney tumors were examined using a T-1 SE sequence (TR/TE 300/10 ms) before and after i.v. administration of 0.1 mmol/kg Gd-DTPA and a T-2 SE sequence (TR/TE 5500/150 ms). The results were correlated with the pathological findings. Results: 38 malignant tumors were found: 29 renal cell carcinomas (RCC), 13 with solid growth, 41 with tubulopapillary growth, and three with mixed growth forms, one cystic RCC, and one chromophobic RCC, in addition, 6 urothelial carcinomas and three other malignomas. Typical MRT criteria for RCC were an inhomogeneity of the tumor with regions of slightly increased signal intensity on the T-1-weighted image (59%) and regions with reduced signal intensity on the T-2-weighted image (96%) as compared with renal parenchyma; these were due to histomorphological hemorrhage and hemosiderin deposits, respectively. A further criterion for RCC was a hypointense pseudocapsule in the T-2 TSE sequence in 79% of the cases. Conclusions: The low-signal nature of RCC in the T-2-weighted image correlates with hemorrhage and hemosiderin deposits. The detection of a pseudocapsule is useful in the differential diagnosis of solid tumors in the kidney.