A case of focal nodular hyperplasia-like lesion presenting unusual signal intensity on the hepatobiliary phase of gadoxetic acid-enhanced magnetic resonance image.

Focal nodular hyperplasia (FNH) or FNH-like lesions of the liver are benign lesions that can be mostly diagnosed by hepatobiliary phase gadoxetic acid-enhanced magnetic resonance imaging (MRI). Accurate imaging diagnosis is based on the fact that most FNHs or FNH-like lesions show characteristic hyper- or isointensity on hepatobiliary phase images. We report a case of an FNH-like lesion in a 73-year-old woman that mimicked a malignant tumor. Dynamic contrast-enhanced computed tomography (CT) and MRI using gadoxetic-acid revealed an ill-defined nodule showing early enhancement in the arterial phase and gradual and prolonged enhancement in the portal and equilibrium/transitional phases. Hepatobiliary phase imaging revealed inhomogeneous hypointensity, accompanied by a slightly isointense area compared to the background liver. Angiography-assisted CT showed a portal perfusion defect of the nodule, inhomogeneous arterial blood supply in the early phase, and less internal enhancement in the late phase, accompanied by irregularly shaped peritumoral enhancement. No central stellate scar was identified in any of the images. Imaging findings could not exclude the possibility of hepatocellular carcinoma, but the nodule was pathologically diagnosed as an FNH-like lesion by partial hepatectomy. In the present case, an unusual inhomogeneous hypointensity on hepatobiliary phase imaging made it difficult to diagnose the FNH-like lesions.