In cases where typical aspects are shown, the diagnosis of most frequent hepatic lesions can be made with some safety by means of several imaging methods; on the other hand, uncommon lesions generally represent a diagnostic challenge for the radiologist. In the present second part of the study, the authors describe four rare hepatic lesions, as follows: primary hepatic lymphoma, myofibroblastic tumor, primary hepatic neuroendocrine tumor and desmoplastic small round cell tumor, approaching their main characteristics and imaging findings with emphasis on computed tomography and magnetic resonance imaging.

Keywords: Neoplasms; Liver; Atypical; Computed tomography; Magnetic resonance imaging.

Recent studies have demonstrated that the use of paramagnetic hepatobiliary contrast agents in the acquisition of magnetic resonance images remarkably improves the detection and differentiation of focal liver lesions, as compared with extracellular contrast agents. Paramagnetic hepatobiliary contrast agents initially show the perfusion of the lesions, as do extracellular agents, but delayed contrast-enhanced images can demonstrate contrast uptake by functional hepatocytes, providing further information for a better characterization of the lesions. Additionally, this intrinsic characteristic increases the accuracy in the detection of hepatocellular carcinomas and metastases, particularly the small-sized ones. Recently, a hepatobiliary contrast agent called gadolinium ethoxybenzyl dimeglumine, that is simply known as gadoxetic acid, was approved by the National Health Surveillance Agency for use in humans. The authors present a literature review and a practical approach of magnetic resonance imaging utilizing gadoxetic acid as contrast agent, based on patients' images acquired during their initial experiment.

Keywords: Magnetic resonance imaging; Gadolinium; Liver; Contrast media.