Multiple Myeloma is a cancer of the blood. Although commonly mistaken by some to be a patient’s bone cancer due to its ability to weaken your bones and reside predominantly in your bone marrow, it is not a primary cancer of the bone. The cell of origin is the plasma cell.
These are very specialized cells that help fight infections by making antibodies. Plasma cells are part of the white blood cell family. These cells start as naïve lymphocytes in your bone marrow. They travel through the blood and lymphatic system to the lymph nodes where they get an education in how to fight specific bacteria by making antibodies against these foreign proteins. Somewhere in this very complex stage of development a mistake happens, leading to a clonal expansion of one plasma cell. This cell then hones back to the bone marrow and grows uncontrollably. One distinguishing feature of this disease is that the abnormal plasma cell continues to make antibodies, usually abnormal ones. This antibody does not function like a normal antibody and cannot help your body fight infections. This antibody is unique to the others produced by the rest of your normal plasma cells and can be measured in the blood, and sometimes the urine, as a specific immunoglobulin protein.
Another name for this is a monoclonal gammopathy, where mono- means one, clonal- means identical, gamma- means immunoglobulin, and pathy- means disease. Your doctor can use measurements of this monoclonal protein in your blood and urine as a marker for your disease and will be following it over time.