Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the stages of Plasma Cell Neoplasms (Including Multiple Myeloma) ?
    ### Response:
    Key Points
                    - There are no standard staging systems for monoclonal gammopathy of undetermined significance (MGUS), macroglobulinemia, and plasmacytoma.    - After multiple myeloma has been diagnosed, tests are done to find out the amount of cancer in the body.
    