Magnetic resonance imaging of cholangiocarcinoma

Cholangiocarcinoma arises from the bile ducts and is the most common primary malignancy of the biliary tree. Cholangiocarcinoma is classified according to its growth pattern: mass-forming, periductal-infiltrating, or intraductal-growing type. The majority of cholangiocarcinomas occur at the common hepatic duct (CHD) and its bifurcation, also referred to as Klatskin's tumor, but they also can occur in more peripheral branches within the hepatic parenchyma. Microscopically, cholangiocarcinoma represents an adenocarcinoma with a glandular appearance arising from the epithelium of the bile ducts. On magnetic resonance (MR) images, cholangiocarcinomas appear hypointense on T1-weighted images, and hyperintense on T2-weighted images. Central hypointensity can be seen on T2-weighted images and correspond to fibrosis. On dynamic MR images, cholangiocarcinomas show moderate peripheral enhancement followed by progressive and concentric filling in the tumor with contrast material. Pooling of contrast within the tumor on delayed MR images is suggestive of peripheral cholangiocarcinoma. The role of MR imaging in hilar cholangiocarcinoma is to confirm/reach a diagnosis and to assess resectability. Hilar cholangiocarcinoma shows the same signal intensity pattern of peripheral tumors both on T1- and T2-weighted images. On magnetic resonance cholangiopancreatography (MRCP) images, hilar cholangiocarcinoma appears as a moderately irregular thickening of the bile duct wall (>/=5 mm) with symmetric upstream dilation of the intrahepatic bile ducts. The aim of preoperative investigation in Klatskin tumors typically requires the evaluation of the level of biliary obstruction, the intrahepatic tumor spread, and the vascular involvement; it also needs to show any atrophy-hypertrophy complex. Because of its intrinsic high tissue contrast and multiplanar capability, MR imaging and MRCP are able to detect and preoperatively assess patients with cholangiocarcinoma, investigating all involved structures such as bile ducts, vessels and hepatic parenchyma. The main reason for surgical/imaging discrepancy is represented by the microscopic diffusion along the mucosa and in the perineural space.