Renal angiomyolipoma with minimal fat.

We report here two patients with angiomyolipoma with minimal fat, who were treated by radical nephrectomy, with a diagnosis of renal cell carcinoma. The tumors in these two patients were hyperattenuated on unenhanced computed tomography (CT) images, but did not show fat components, and were moderately enhanced on contrast-enhanced CT images. The tumor in one patient was homogeneously hypointense on T2-weighted magnetic resonance (MR) images, enhanced during the early phase on dynamic MR images, and, further, showed abundant pulsatile blood vessels on color Doppler examination. These imaging findings of renal tumors suggested the possibility of angiomyolipoma with minimal fat; accordingly, when imaging results suggest this possibility, further careful sampling to identify minimal fat components must be performed by thin-section unenhanced CT.