Features of a perihilar cholangiocarcinoma, also known as Klatskin tumor. It may be challenging to visualize the mass, as it is usually ill-defined and most of the imaging features are indirect signs of tumor development such as biliary duct dilatation, vascular involvement, or regional lymphadenopathy.

In this case, the tumor probably arises from the left hepatic duct (left portal vein invasion, lobe atrophy and marked ipsilateral intrahepatic ducts dilatation) with a later invasion of the right hepatic bile duct.