Differentiating mass-forming intrahepatic cholangiocarcinoma from atypical hepatocellular carcinoma using Gd-EOB-DTPA-enhanced magnetic resonance imaging combined with serum markers in at-risk patients with hepatitis B virus.

Background: The precise differentiation of intrahepatic cholangiocarcinoma (ICC) from atypical hepatocellular carcinoma (HCC) is vital for treatment strategy and prognostic prediction. In clinical practice, nearly 40% of HCCs demonstrate atypical manifestations, particularly HCCs with rim arterial phase hyperenhancement (APHE), which is challenging to differentiate from mass-forming ICC. Thus, we aimed to develop a diagnostic regimen of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) contrast-enhanced magnetic resonance imaging (MRI) combined with serum tumor markers in differentiating mass-forming ICC from atypical HCC in at-risk patients with the hepatitis B virus (HBV). Methods: This study enrolled 129 patients with pathologically proven mass-forming ICCs (n=53) and atypical HCCs (n=76) who had undergone preoperative Gd-EOB-DTPA contrast-enhanced MRI. The clinical data and imaging findings were analyzed. Univariate and multivariate logistic analyses were performed to identify the independent predictors for differentiating mass-forming ICCs from atypical HCCs. The diagnostic performance was evaluated using receiver operating characteristic (ROC) curves, and DeLong test was used to compare the areas under curves of all independent predictors. Results: Univariate logistic regression analysis revealed normal alpha fetoprotein (AFP), elevated carbohydrate antigen 19-9 (CA19-9) level, elevated carcinoma embryonic antigen (CEA) level, central hyperintensity on T2-weighted imaging (T2WI), central hypointensity on T2WI, and targetoid sign on hepatobiliary phase (HBP) and targetoid restriction on diffusion-weighted imaging (DWI) were more likely to be significant predictors favoring mass-forming ICCs (all P values <0.05). In contrast, multifocal hyperintensity on T2WI and capsule sign were more frequently seen in patients with atypical HCC (all P values <0.05). Multivariate analysis revealed normal AFP, elevated CA19-9 level, targetoid sign on HBP, and targetoid restriction on DWI (all P=0.001) were independent predictors for differentiating mass-forming ICCs from atypical HCCs; DeLong test showed that the area under curve (AUC) increased to 0.949 when the above predictors were combined (all P values <0.05), and the sensitivity, specificity, and accuracy of the combined independent predictors were 88.7%, 93.4%, and 91.5%, respectively. Conclusions: A diagnostic regimen integrating tumor markers (AFP, CA19-9) and imaging biomarkers (targetoid restriction on DWI and/or targetoid sign on HBP) using Gd-EOB-DTPA-enhanced MRI could help to differentiate mass-forming ICCs from atypical HCCs and achieve high diagnostic performance of mass-forming ICCs in at-risk patients with the HBV. Keywords: Mass-forming intrahepatic cholangiocarcinoma (mass-forming ICC); atypical hepatocellular carcinoma (atypical HCC); magnetic resonance imaging (MRI); gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA); hepatobiliary phase (HBP).