News on Benign Liver Lesions

Differentiation between the benign liver lesion focal nodular hyperplasia (FNH) and hepatocellular adenomas (HCAs) is made easier by gadoxetate disodium-enhanced MRI and careful image interpretation.

Focal nodular hyperplasia (FNH) is the second most common benign liver tumor, while hepatic adenomas (HCA) are rather rare. HCAs are also benign, yet three of the eight subtypes carry a high risk of malignant transformation, making differentiation between FNH and HCAs important. Ahmed Ba-Ssalamah, Medical University of Vienna. Austria, shared the diagnostic options with his audience.

Contrast-enhanced MRI is better

A meta-analysis of FNH diagnosis with gadoxetate disodium (Primovist^®) showed in 2008 that enhanced MRI is better than unenhanced MRI or CT (Zech C et al. 2008). A recent prospective study (Nowicki TK et al., 2018) confirmed the superiority of a hepatobiliary MR contrast agent to multi-phase CT in differential diagnosis of FNH.

Uptake mechanism of gadoxetate disodium (Primovist^®)

Both FNH and HCA are cholestatic liver lesions, meaning that they are not linked to the bile duct by the bile flow. However, the receptor expression of OATP and MRP3, responsible for the uptake and clearance of gadoxetate disodium, differs between FNH and HCAs. These differences show in hepatobiliary contrast enhancement.

Differentiating with gadoxetate disodium (Primovist^®) -enhanced MRI

Purysko AS et al. found in 2012 that FNH enhances significantly more than hepatocellular adenoma on gadoxetate disodium-enhanced MRI. The most pronounced difference in enhancement ratio was measured in the arterial phase. Purysko could also define an HBP-threshold with high sensitivity and specificity for differentiating between FNH and HCA. Bieze M et al. confirmed the accuracy of gadoxetate disodium-enhanced MRI for the differentiation. With standard MRI, 40% of all cases remained inconclusive about the diagnosis. Contrast-enhanced MRI left no uncertainties in lesions larger than two centimeters.

In a recent paper, Guo Y et al. (2017) could even differentiate between HCA-subtypes. The low signal intensity on the HBP of gadoxetate disodium -MRI could identify steatotic HCA to a 100%, unclassified HCA to 92%, inflammatory HCA to 75%, and ß-catenin HCA to 59%.

Conclusion

Ba-Ssalamah focussed on the differential diagnosis of FNH and HCA as well as on HCA subtypes by mainly relying on hepatobiliary contrast-enhanced MRI. However, he underlined to take risk factors and other imaging findings into account for the final diagnosis.