Cholangiocarcinoma is a malignant tumor originating from the extrahepatic bile duct including the hilar region to the lower bile duct of the common bile duct. The incidence of bile duct cancer is more common in men than in women, about 55%-60%, and the average age of onset is about 57 years. The etiology of cholangiocarcinoma is not clear. It may be related to the following factors: 1. bile duct stones About 1/3 of bile duct cancer patients are combined with bile duct stones, and 5%-10% of bile duct stone patients will develop bile duct cancer, which means that the bile duct is stimulated by stones for a long time and the epithelium undergoes proliferative changes, which may be related to the development of bile duct cancer. 2.Cystic dilatation of bile ducts Cancer occurs in patients with cystic dilatation of bile ducts. Stone formation and bacterial infection in the cyst, especially the reflux of pancreatic juice due to abnormal development of the confluence, are the main causes of carcinogenesis, and patients with the disease should have their bile duct cysts completely removed as soon as possible. 3.Biliary parasites (such as Toxoplasma gondii) 4.Primary sclerosing cholangitis