Kiatskin tumor is:

Ans: A (Common hepatic duct tumor) Ref: Robbins Pathologic basis of Disease. 8th ed.Explanation:Klatskin tumor (or hilar cholangiocarcinoma)It is a cholangiocarcinoma (cancer of the biliary tree) occurring at the confluence of the right and left hepatic bile ducts.Cancer of the bile duct, cholangiocarcinoma, can occur anywhere along the biliary tract front the ampulla of Vater to the intrahepatic biliary radicals.The hepatic duct bifurcation is the most frequently involved site accounting for approximately 60-80% of cholangiocarcinomas.Primary sclerosing cholangitis, an idiopathic inflammatory condition of the biliary tree, has been clearly associated with the development of cholangiocarcinoma in up to 40% of patients.Congenital biliary cystic disease, such as choledochal cysts or Caroli's disease, has also been associated with malignant transformation in up to 25% of cases.Chronic biliary tract parasitic infection, seen commonly in Southeast Asia due to Clonorchis sinensis and Opisthorchis vivemni. has also been identified as a risk factor.Although gallstones and cholecystectomy are not thought to be associated with an increased incidence of cholangiocarcinoma, hepatolithiasis and choledocholithiasis may predispose to malignant change.Finally, industrial exposure to asbestos and nitrosamines, and the use of the radiologic contrast agent, Thorotrast (thorium dioxide), are considered to be risk factors for the development of cholangiocarcinoma.