Hepatocellular carcinoma with hilar bile duct tumor thrombus versus hilar Cholangiocarcinoma on enhanced computed tomography: A diagnostic challenge

Background: Hepatocellular carcinoma (HCC) with hilar bile duct tumor thrombus (HBDTT) often mimic hilar cholangiocarcinoma (hilar CC). The purpose of this study is to analyze the Computed Tomography (CT) characteristics of HCC with HBDTT and to identify imaging features to aid its differentiation from hilar CC on enhanced CT. Methods: We retrospectively identified 58 cases with pathologically proved HCC with HBDTT between 2011 and 2018. Seventy-seven cases of pathologically proven hilar CCs were selected during the same period. The clinical features and CT findings of the two groups were reviewed and compared. Results: HCC with HBDTTs are more commonly found in men (87.9% vs 63.6%, p = 0.001) with lower age of onset (49.84 vs 58.61 years; p < 0.001) in comparison to hilar CCs. Positive correlation were identified between HCC with HBDTTs and chronic HBV infection (72.4% vs 11.7%; p < 0.001), increased serum AFP (67.2% vs 1.3%; p < 0.001), CA19-9 level (58.6% vs 85.7%; p < 0.001) and CEA level (3.4% vs 29.9%; p = 0.001), parenchymal lesion with intraductal lesion (100% vs 18.2%; p < 0.001), washout during the portal venous phase (84.5% vs 6.5%; p < 0.001), thickened bile duct wall (8.6% vs 93.5%; p < 0.001), intrahepatic vascular embolus (44.8% vs 7.8%; p < 0.001), splenomegaly (34.5% vs 2.6%, p < 0.001). A scoring system consisting of the five parameters obtained from characteristics mentioned above was trialed. The sensitivity and specificity for diagnosing HCC with HBDTT were 96.39, 100 and 92.5% respectively when the total score was 2 or more. Conclusions: HCC with HBDTTs are often distinguishable from hilar CCs based on washout during portal venous phase without thickened bile duct wall. HBV infection and serum AFP level facilitate the differentiation.