Imaging modalities for focal nodular hyperplasia and hepatocellular adenoma

There are several imaging modalities available for the detection of focal liver lesions. Differentiation between focal nodular hyperplasia (FNH) and hepatocellular adenoma (HCA) is important because of the consequences for management. However, differentiation based on imaging alone still shows limitations.

We reviewed the literature for typical features of FNH and HCA on radiologic and nuclear imaging with emphasis on differentiation of both lesions.

Seven articles describe the performance of an imaging modality for the differentiation between FNH and HCA. Limitations of these studies are the small sample size and/or the lack of comparison with the 'gold standard', i.e. histological diagnosis. No studies are available that compare the accuracy of several imaging modalities in the differentiation of FNH and HCA. Conventional ultrasound (US) is not useful in the differentiation because of the non-specific features. On contrast-enhanced US, the arterial filling direction of FNH is centrifugal and centripetal in case of HCA. The parenchymal enhancement of FNH is sustained in the portal venous and delayed phases, but shows rapid washout in case of HCA. Multiphase CT scan can differentiate FNH from HCA when there is a central scar. FNH may have a slightly higher relative enhancement in the arterial phase. On MRI with hepatocyte-specific contrast agents, HCA does not show contrast uptake in the hepatobiliary phase in contrast to FNH.

We conclude that there is limited evidence of the diagnostic performance of currently used imaging modalities for the differentiation of FNH and HCA. We therefore propose a prospective study (DiFA trial) to determine the accuracy of several radiologic and nuclear imaging studies in differentiating FNH and HCA.