Fat-containing lesions of the liver: radiologic-pathologic correlation.

Fat-containing tumors of the liver are a heterogeneous group of tumors with characteristic histologic features, variable biologic profiles, and variable imaging findings. Benign liver lesions that contain fat include focal or geographic fatty change (steatosis), pseudolesions due to postoperative packing material (omentum), adenoma, focal nodular hyperplasia, lipoma, angiomyolipoma, cystic teratoma, hepatic adrenal rest tumor, pseudolipoma of the Glisson capsule, and xanthomatous lesions in Langerhans cell histiocytosis. Malignant liver lesions that can contain fat include hepatocellular carcinoma, primary and metastatic liposarcoma, and hepatic metastases. Identification of fat within a liver lesion can be critical in characterization of the lesion. The imaging characteristics of a lesion coupled with the pattern of intratumoral fatty change are helpful in narrowing the differential diagnosis. Although the presence of fat can be demonstrated with computed tomography or ultrasound, magnetic resonance imaging is the most specific imaging technique for demonstration of both microscopic and macroscopic fat.