Large hepatic focal lesion in segment VIII, showing initial T1 iso-density, however it is clearly identified on DWI. It also show average post contrast enhancement in the hepatic parenchymal phase together with a central non enhancing region (central scar). The lesion shows rather benign features and no compression or invasion to the nearby IVC or hepatic veins.
This mass does not show hypervascular enhancement in the arterial phase, since the arterial phase was very early, but FNH is classically an arterially enhancing lesion. Hepatocellular carcinoma is also an arterially-enhancing lesion, and the two entities are differentiated on the delayed phases: FNH fades to background signal intensity and HCC "washes out" relative to background.
In out-of-phase MRI sequence then mass shows no significant signal drop denoting no intracellular fat contents, which would have been the case if this was a hepatic adenoma. The presence of a central scar is a typical finding in Focal nodular hyperplasia (FNH), together with the previous exclusions, aid to the diagnosis of FNH with confidence, despite the fact that this is a male patient, as FNH has a high predilection to females.