Hypointense renal cell carcinoma: MR imaging with pathologic correlation. In two pathologically documented cases of renal cell carcinoma, the appearance of the tumors at magnetic resonance (MR) imaging was markedly hypointense relative to normal renal parenchyma on both T1- and T2-weighted spin-echo images. Pathologic examination of both tumors revealed diffuse iron scattered throughout the tumors. The paramagnetic effect of the iron may account for this unusual hypointense appearance at spin-echo imaging, independent of pulse sequence. 