Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Klatskin tumor ?
    ### Response:
    Klatskin tumors are tumors that affect the upper part of the bile duct where it divides to enter the right and left parts of the liver. One or both sides may be affected. Individuals with Klatskin tumors often present with jaundice and/or abnormal liver tests.
    