State-of-the-art MR imaging of fat-containing focal lesions of the liver

BACKGROUND: Fat can be identified in numerous liver lesions, and usually is not a specific finding. Distinguishing between different kinds of fatty deposits is an important part of differential diagnosis. Magnetic Resonance Imaging (MRI) is superior to other imaging techniques because it allows distinguishing intracellular from macroscopic fat. DISCUSSION: Intracellular lipid may be found in focal hepatic steatosis, hepatic adenoma, hepatocellular carcinoma and, less commonly, in focal nodular hyperplasia as well as regenerative and dysplastic nodules. Macroscopic fat is seen in angiomyolipoma, lipoma, metastases from fatcontaining neoplasms, primary or metastatic liposarcoma, hydatid cyst, pseudolipoma of the Glisson capsule, pericaval fat collection, lipopeliosis, hepatic teratoma, focal hepatic extramedullary haematopoiesis and adrenal rest tumour. CONCLUSION: Liver nodules should be characterised with regard to underlying liver condition, MRI characteristics and contrast enhancement pattern, including hepatobiliary phase. In many cases, identification of fatty content may help narrowing the differential diagnosis.