Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the stages of Pituitary Tumors ?
    ### Response:
    Key Points
                    - Once a pituitary tumor has been diagnosed, tests are done to find out if it has spread within the central nervous system (brain and spinal cord) or to other parts of the body.     - Pituitary tumors are described in several ways.
    