This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Anatomy
Klatskin tumor is 
Select and explain. 
A. Merkel cell carcinoma of skin, B. Primitive neuroectodermal tumor of chest wall, C. Common hepatic duct tumor, D. Adenocarcinoma of anal cancer
C: Common hepatic duct tumor
Answer: C: Common hepatic duct tumor 
Explanation: Hilar cholangiocarcinoma is also known as Klatskin tumor Bismuth - corlette classification of Hilar Cholangiocarcinoma Type I- Tumor confined to hepatic duct, not involving the main biliary confluence Type II- Tumor involving the main biliary confluence but not extending to the right or left ducts Type IIIa- Tumor extending upto the right secondary biliary confluence Type IIIb- Tumor extending upto the left secondary biliary confluence Type IV - Tumor extending bilaterally to the secondary biliary confluence Ref : Sabiston 20th edition Pgno :1514-1518