Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Adult Central Nervous System Tumors ?
    ### Response:
    Key Points
                    - An adult central nervous system tumor is a disease in which abnormal cells form in the tissues of the brain and/or spinal cord.    - A tumor that starts in another part of the body and spreads to the brain is called a metastatic brain tumor.
    