Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Kaposi sarcoma ?
    ### Response:
    Kaposi sarcoma (KS) is a cancer that develops from the cells that line lymph or blood vessels. It usually appears as tumors on the skin or on mucosal surfaces such as inside the mouth, but tumors can also develop in other parts of the body (including the lymph nodes, lungs, or digestive tract).
    