How to utilize LR-M features of the LI-RADS to improve the diagnosis of combined hepatocellular-cholangiocarcinoma on gadoxetate-enhanced MRI?

OBJECTIVES: To investigate the diagnostic accuracy of each LR-M feature defined in version 2017 of the Liver Imaging Reporting and Data System (LI-RADS) and determine the optimal LR-M feature for differentiating combined hepatocellular-cholangiocarcinoma (cHCC-CCA) and hepatocellular carcinoma (HCC) on gadoxetate-enhanced magnetic resonance imaging (MRI). METHODS: Ninety-nine patients with pathologically proven cHCC-CCA (n = 33) or HCC (n = 66) after surgery were identified. Two radiologists retrospectively assessed preoperative gadoxetate-enhanced MRI for features favoring non-HCC malignancies (LR-M features) according to LI-RADS version 2017. Multivariate logistic regression analysis was performed to determine the independent differential features. The sensitivity and specificity for diagnosing cHCC-CCA were calculated for each LR-M feature. RESULTS: Targetoid appearance showed the highest sensitivity (75.8%, 95% confidence interval [CI] 60.6%, 87.3%) to correctly identify cHCC-CCA as LR-M. At least one LR-M feature was observed in 31 (93.9%) patients with cHCC-CCA and 34 (51.5%) patients with HCC. The sensitivity and specificity for diagnosing cHCC-CCA using the presence of any one of the LR-M features were 93.9% (95% CI 80.7, 98.9) and 48.5% (95% CI 41.9, 51.0), respectively. The presence of three LR-M features yielded the highest diagnostic accuracy of 80.8% (95% CI 72.1, 86.1) with a reduced sensitivity of 54.5% (95% CI 41.4, 62.5). CONCLUSION: The majority of cHCC-CCA cases can be properly categorized as LR-M when any one of the LR-M features defined in the LI-RADS version 2017 is used as a determiner. However, approximately half of HCC cases also show at least one LR-M feature. KEY POINTS: • Targetoid appearance, including rim APHE, peripheral "washout" appearance, and delayed central enhancement, was the LR-M feature that identified cHCC-CCA as a non-HCC malignancy with the highest sensitivity. • Most cHCC-CCA cases can be properly categorized as LR-M when the presence of any one of the LR-M features was used as the determiner. • Approximately half of HCC cases also showed at least one LR-M feature.