Hepatic Angiomyolipoma with Minimal Intratumoral Fat Content

We report a rare case of hepatic angiomyolipoma with minimal fat content. The low fat content led to an incorrect preoperative diagnosis. A 38-year-old man who was a carrier of hepatitis B virus infection incidentally presented with a hepatic tumor. His serum alpha-fetoprotein level was normal. Ultrasonography revealed a well-circumscribed, heterogeneous hypoechoic nonencapsulated liver tumor measuring 34 × 24 mm. Precontrast computed tomography (CT) did not reveal fatty attenuation in the lesion. Contrast-enhanced CT revealed a hypervascular nonencapsulated tumor in the arterial phase and moderate washing out of the contrast medium in the portal phase. A hypervascular tumor was observed on CT hepatic arteriography, and complete washing out of the contrast medium on CT during arterial portography. These findings are compatible with hepatocellular carcinoma. The tumor exhibited low signal intensity on T1-weighted images and high signal intensity on T2-weighted images; no hypointensity was observed on fat suppression images. The patient underwent left hemihepatectomy because of a preoperative diagnosis of hepatocellular carcinoma. The histopathological diagnosis was a hepatic angiomyolipoma with 5% fat content. Low fat content makes the diagnosis of this condition difficult. The absence of serum tumor markers and the presence of a nonencapsulated hypervascular tumor may facilitate the accurate preoperative diagnosis of hepatic angiomyolipomas that have a low fat content and mimic hepatocellular carcinoma.