Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Merkel cell carcinoma ?
    ### Response:
    Merkel cell carcinoma (MCC) is a rare type of skin cancer that usually appears as a single, painless, lump on sun-exposed skin. It is typically red or violet in color. It is considered fast-growing and can spread quickly to surrounding tissues, nearby lymph nodes, or more distant parts of the body.
    