A case of angiomyolipoma diagnosed by thin slice non-enhanced CT and needle biopsy.

We report a case of a 52-year-old female with two intrarenal tumors in the left kidney and a contralateral non-functioning kidney. Two renal cell carcinomas were suspected on 10mm and 5mm thick slices of computed tomography (CT), while angiography could not exclude a diagnosis of angiomyolipoma. Thin section (2 mm thick) non-enhanced CT detected negative attenuation values (indicative of fat) within both tumors, but these values were higher than the value for normal fat tissue. Negative attenuation values within the tumor using non-enhanced thin sections are thought to be essential for a CT diagnosis of angiomyoplipoma, especially when angiomyolipoma is difficult to distinguish from renal cell carcinoma. We performed an ultrasonography-guided needle biopsy of the tumor and pathological examination confirmed the diagnosis of angiomyolipoma, consisting of rich angiomyomatous element and small amount of mature adipose tissue.