They are an integral part of the immune system . The antibodies produced are specific to attack a particular kind of germ or foreign tissue. Plasmacytoma is basically a cancer of the plasma cells, meaning that they are multiplying out of control.
Cells commonly divide rapidly in womb life, childhood and puberty, to grow the adult body.
After this, most divide more slowly to replace cells lost through old-age or injury. Blood cells, which include red cells to carry oxygen, white cells to fight infection, and platelets for clotting, continue to divide rapidly in adults, for these cells are usually short-lived. For the immune system, a great quantity of specific antibody is only needed to fight a specific invader, since the antibody produced for each type of germ is different. Thus, only particular white blood cells will be needed in large quantity. A cancer of the the immune system starts in just one cell .