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Background: Angiomyolipoma (AML) is the most common renal tumor in tuberous sclerosis (TS) patients. However, these patients also face an increased risk of malignant kidney neoplasms. Case report: A 7-year-old boy with a diagnosis of TS was sent for abdominal CT due to a single isoechoic tumor in the lower pole of left kidney, which was revealed in US. CT exam confirmed the presence of a hiperdense tumor which exceeded margins of the left kidney. The tumor was homogenously enhanced after contrast administration. The absence of regions of negative attenuation in CT and the isoechogenisity in US suggested rather malignant lesion than AML. Partial nephrectomy was performed. Subsequent pathologic examination classified the tumor as a low-fat AML. Conclusions: Radiological diagnosis of low-fat AML is difficult and requires a careful differentiation from other lesions.