Cholangiocarcinomas are malignancies of the biliary duct system that may originate in the liver and extrahepatic bile ducts, which terminate at the ampulla of Vater.
Cholangiocarcinoma are encountered in 3 regions: intrahepatic, extrahepatic (ie, perihilar), and distal extrahepatic.
Intrahepatic cholangiocarcinoma arises from small intrahepatic bile duct branches and invades adjacent liver parenchyma Perihilar tumors, also called Klatskin tumors (after Klatskin\'s description of them in 1965), occur at the bifurcation of right and left hepatic ducts .The distal extrahepatic type includes tumors that arise from extrahepatic ducts from the level of the upper border of the pancreas to the ampulla of vater. Perihilar tumors are the most common, and intrahepatic tumors are the least common.
Pathophysiology: Cholangiocarcinoma is a tumor that arises from the intrahepatic or extrahepatic biliary epithelium. More than 90% are adenocarcinomas, and the remainder are squamous cell tumors.
Symptoms may include jaundice, clay-colored stools, bilirubinuria (dark urine), pruritus, weight loss, and abdominal pain.
Causes: The etiology of most bile duct cancers remains undetermined.
Infections - chronic infections with liver flukes, Clonorchis sinensis, and Opisthorchis viverrini and parasite, Ascaris lumbricoides, have been implicated in the pathogenesis.
Inflammatory bowel disease - CCC generally develops in patients with long-standing ulcerative colitis and PSC.
Chemical exposures - Certain chemical exposures have been implicated in the development of bile duct cancers, primarily among workers in the aircraft, rubber, and wood finishing industries.
Congenital diseases of the biliary tree, including choledochal cysts and Caroli disease, have been associated with CCC.
Other conditions rarely associated with CCC include bile duct adenomas, biliary papillomatosis, and alpha1-antitrypsin deficiency.
IMAGING: MRI Signal intensity and enhancement patterns:
Typically, the tumor is hypointense on T1-weighted (T1W), and hyperintense on T2-weighted (T2W) imaging relative to liver parenchyma.
The degree of hyperintensity on T2W imaging is variable and has been described as mild, moderate, or marked. This variability is mostly due to the amount of fibrosis, necrosis, and mucin within the tumor, and is influenced by the subtype of the tumor: well-differentiated adenocarcinoma shows higher signal intensity on T2W imaging compared to the scirrhous subtype, which has more fibrosis, less mucin and necrosis
Cholangiocarcinoma is a hypovascular tumor, and following the intravenous administration of gadolinium chelates, the classic enhancement pattern of cholangiocarcinoma is heterogeneous or homogeneous with progressive and prolonged delayed enhancement.
Four patterns of enhancement of cholangiocarcinoma have been described on early (30 s), late (1 and 3 min) and delayed (5 min) post-gadolinium imaging:
- Early peripheral enhancement with progressive and concentric filling in, which is the most common enhancement pattern.
- Early peripheral enhancement with non-filling of the central area of the tumor (central scar).
- Progressive and complete enhancement.
- Early, marked, and complete enhancement, followed by heterogeneous washout of contrast, usually from the periphery of the tumor; this is the least common enhancement pattern.
The variable enhancement pattern of cholangiocarcinoma is related to the amount and distribution of tumor cells and fibrous tissue in the tumor.
Progressive and prolonged enhancement is seen in areas of fibrosis where there is decreased arterial blood supply, and large interstitial spaces .
Early enhancement and late phase peripheral washout has been shown to correspond to regions of tumor cells, and reflect hypervascularity and increased perfusion. Occasionally, a thin rim of enhancement is seen around the tumor on late phase gadolinium-enhanced imaging, which reflects decreased arterial inflow and washout in a region of congested liver with dilated sinusoids around the tumour.