Fatty metamorphosis in hepatocellular carcinoma: radiologic features in 10 cases.

We describe the sonographic, CT and angiographic findings in 10 cases of hepatocellular carcinoma in which extensive fatty metamorphosis occurred within the tumors. Fatty change was diffuse in smaller tumors (less than 3.5 cm) and focal in larger tumors (greater than 3.5 cm). Fatty metamorphosis characteristically caused a low-attenuation area on CT (less than -10 H) and a highly echogenic area on sonography. The sonographic appearance of small hepatocellular carcinomas with fatty metamorphosis was identical to the findings in cavernous hemangioma or focal fatty change of the liver. CT correctly revealed the presence of fat in these hepatocellular carcinomas. In these cases, hepatic arteriography showed no tumor stain; however, CT arteriography (dynamic CT during injection of contrast medium into the hepatic artery) was useful in showing the tumor, its capsule, and its internal septa. In the diagnosis of large hepatocellular carcinoma, the presence of intratumoral fat is not likely to be problematic, but small tumors that are diffusely infiltrated by fat must be distinguished from such benign conditions as focal fatty change, lipoma, and angiomyolipoma.