Systematics of Imaging Morphology

Among benign liver tumors, hemangiomas and focal nodular hyperplasia (FNH) are by far the most commonly detected, being associated in 20 % of cases; due to specific imaging features such as the pattern of contrast enhancement and tumor morphology, the diagnosis of these benign tumors in most cases is confidently carried out with contrast-enhanced US, MRI, or CT with no need for percutaneous biopsy or surgical resection. Hepatic adenomas are rare entities that in many cases show specific imaging features related to the intracellular accumulation of fat or glycogen and to the presence of various degrees of hemorrhage, necrosis, and calcifications, better investigated with magnetic resonance and, in particular, with the chemical shift technique. Hepatic cysts are not considered liver tumors unless they must be differentiated from biliary cystadenoma and cystic metastases. Hepatic hemangiomas shows a typical pattern on T2w images and on contrast-enhanced study. Further information in the distinction of these lesions is provided by the hepatobiliary phase at MRI with hepatocyte-specific contrast agents: while FNH is inconstantly hyperintense to the liver, all the other tumors tend to be markedly hypointense, lacking the intracellular accumulation of the contrast agent.