Epidemiology and risk factors: intrahepatic cholangiocarcinoma.

Intrahepatic cholangiocarcinoma (ICC) is a rare entity with a distinct clinical course and epidemiology from hilar and extrahepatic cholangiocarcinoma. ICC makes up 8-10% of cholangiocarcinomas and 10-20% of all primary liver tumors. There remains a considerable amount of geographic variation in the incidence of ICC worldwide; however, the overall incidence of this malignancy appears to be rising. Several risk factors have been identified, such as infectious causes (liver flukes, viral hepatitis), biliary tract disease [primary sclerosing cholangitis (PSC), hepaticolithiasis, biliary cystic diseases], metabolic syndrome, lifestyle choices (alcohol abuse, tobacco use), and cirrhosis. Despite this, a substantial number of ICC patients do not have any identifiable risk factors, underlining the need for further work into the pathogenesis of this malignancy.