ANGIOMYOLIPOMA - IMAGING FINDINGS IN LESIONS WITH MINIMAL FAT

PURPOSE: To investigate a method of diagnosing angiomyolipoma that con tains minimal fat. MATERIALS AND METHODS: In six cases of angiomyolipo ma with minimal fat, the attenuation on contrast material-enhanced and unenhanced computed tomographic (CT) images, the echogenicity on sono grams, the signal intensity on T2-weighted magnetic resonance (MR) ima ges, and the gross configuration of the lesion were retrospectively an alyzed. In 100 cases of renal cell carcinoma, the same parameters were analyzed, and results were compared with those of angiomyolipoma. RES ULTS: When compared with the surrounding renal parenchyma, all six ang iomyolipomas showed homogeneously high attenuation on unenhanced CT im ages, homogeneous enhancement on contrast-enhanced CT images, and homo geneous isoechogenicity on sonograms. Of the five angiomyolipomas exam ined with MR imaging, four were hypointense and one was isointense on T2-weighted images. All six angiomyolipomas protruded from the renal m argin. None of the 100 renal cell carcinomas showed homogeneously high attenuation on unenhanced CT images, homogeneous enhancement on contr ast-enhanced CT images, or homogeneous isoechogenicity on sonograms. C ONCLUSION: In the kidney, homogeneously high attenuation on unenhanced CT images, homogeneous enhancement on contrast-enhanced CT images, an d homogeneous isoechogenicity on sonograms are suggestive of angiomyol ipoma that contains abundant muscle and minimal fat.