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Potential to Avoid Invasive Procedures for Atypical Focal Nodular Hyperplasia (FNH) and FNH-like Lesions Based on MR
Hanae Hasegawa1, Kumi Ozaki1, Kenichi Harada2
1Department of Radiology, Hamamatsu University School of Medicine, Hamamatsu Shizuoka, Japan.
Purpose:
To identify the imaging characteristics of rare, histopathologically confirmed focal nodular hyperplasia (FNH) and FNH-like lesions (FNH/FNH-like lesions) and determine whether invasive procedures could have been avoided by comprehensive MRI review.
Methods:
We retrospectively enrolled patients with pathologically confirmed FNH/FNH-like lesions between January 2011 and December 2023. These cases underwent biopsy or resection due to their atypical hepatobiliary phase appearance. Six patients with hepatocellular carcinoma (HCC) were included from a separate cohort for comparison. Gadoxetic acid-enhanced MRI findings were qualitatively evaluated. Apparent diffusion coefficient (ADC) values and enhancement during the hepatobiliary phase were quantitatively assessed, and the relative enhancement ratio (RER) to liver parenchyma and intrahepatic vessel (RERv) was calculated. Organic anion transporting polypeptides (OATP)1B3 expression was confirmed histopathologically.
Results:
Five patients with FNH/FNH-like lesions and 6 patients with HCC were evaluated. The non-contrast MRI findings were non-specific for both groups. All 5 FNH/FNH-like lesions displayed non-rim arterial phase hyperenhancement (APHE) without washout during dynamic contrast study with ADC values of 1.162 ± 0.124 × 10-3mm2/sec (mean ± standard deviation). Whereas all 6 HCCs displayed non-rim APHE and washout with ADC values of 0.923 ± 0.138 × 10-3mm2/sec. During the hepatobiliary phase, all 5 FNH/FNH-like lesions were hypointense to the liver but hyperintense to intrahepatic vessels, with RER and RERv ≥ 0.90, indicating preserved gadoxetic acid uptake. OATP1B3 membrane expression was confirmed. By contrast, 5 HCCs were hypointense to both the liver and vessels, with RER and RERv < 0.90 and no OATP1B3 expression.
Conclusion:
FNH/FNH-like lesions with hepatobiliary phase hypointensity, the characteristic finding of hyperintensity relative to intrahepatic vessels distinguished them from similarly presenting HCCs. Careful evaluation of this specific imaging feature might have potentially avoided the need for invasive treatment or biopsy in these diagnostically challenging cases.
Insights
Focal nodular hyperplasia (FNH) and FNH-like lesions show characteristic hepatobiliary phase enhancement patterns on MRI. Hyperintensity relative to intrahepatic vessels can help differentiate these from hepatocellular carcinoma (HCC), potentially avoiding invasive procedures.
Area of Science:
- Hepatobiliary imaging
- Diagnostic radiology
- Oncology
Background:
- Focal nodular hyperplasia (FNH) and FNH-like lesions can present atypically on MRI.
- Distinguishing these from hepatocellular carcinoma (HCC) is crucial for appropriate patient management.
- Invasive procedures like biopsy are sometimes performed due to diagnostic uncertainty.
Purpose of the Study:
- To identify imaging characteristics of focal nodular hyperplasia (FNH) and FNH-like lesions.
- To determine if comprehensive MRI review could prevent unnecessary invasive procedures.
- To compare MRI findings of FNH/FNH-like lesions with hepatocellular carcinoma (HCC).
Main Methods:
- Retrospective analysis of pathologically confirmed FNH/FNH-like lesions and HCC cases.
- Gadoxetic acid-enhanced MRI evaluation, including qualitative and quantitative assessment.
- Measurement of apparent diffusion coefficient (ADC) values and relative enhancement ratios (RER, RERv).
- Histopathological confirmation of Organic anion transporting polypeptides (OATP)1B3 expression.
Main Results:
- FNH/FNH-like lesions showed non-rim arterial phase hyperenhancement (APHE) without washout and specific hepatobiliary phase enhancement (RER/RERv ≥ 0.90), indicating preserved gadoxetic acid uptake and OATP1B3 expression.
- Hepatocellular carcinoma (HCC) cases demonstrated APHE with washout and hypointensity in the hepatobiliary phase (RER/RERv < 0.90) with absent OATP1B3 expression.
- Non-contrast MRI findings were non-specific for differentiating the groups.
Conclusions:
- Hepatobiliary phase hyperintensity relative to intrahepatic vessels is a key differentiator for FNH/FNH-like lesions compared to HCC.
- Careful evaluation of this specific MRI feature may avoid invasive procedures in diagnostically challenging cases.
- Preserved gadoxetic acid uptake, reflected in OATP1B3 expression, is characteristic of FNH/FNH-like lesions.
