Cholangiocarcinoma: epidemiology, risk factors, pathogenesis, and diagnosis.

Cholangiocarcinoma (CCA) is a rare tumor arising from the epithelium of the intrahepatic or the extrahepatic bile ducts. It is rarely diagnosed before 40 years of age except in patients with primary sclerosing cholangitis. CCA is usually clinically silent until the tumor obstructs the bile ducts. Carbohydrate antigen 19-9 is the most commonly used tumor marker, and magnetic resonance cholangiopancreatography is the best available imaging modality for CCA. Endoscopic retrograde cholangiopancreatography and cholangioscopy allow tissue acquisition. Positron emission tomography may play a role in identifying occult metastases. Tissue diagnosis is obtained by brush cytology or bile duct biopsy.