Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Plasma cell leukemia ?
    ### Response:
    Plasma cell leukemia (PCL) is a rare and aggressive form of multiple myeloma that involves high levels of plasma cells circulating in the peripheral blood. The signs and symptoms of PCL include aggressive clinical features, such as extramedullary disease, bone marrow failure, advanced stage disease and expression of distinct immunophenotypic markers.
    