This article is a sidebar to "Banking on DNA: Scientists pool genetic information for myeloma research," published in the University of Minnesota Cancer Center 2007 Annual Report.

Multiple myeloma is a cancer of plasma cells in the blood. Normal plasma cells derive from a type of white blood cell and are typically found within bone marrow. Plasma cells play a role in the immune system by secreting antibodies that circulate in the blood. When foreign substances such as bacteria or viruses enter the body, they stimulate the plasma cells to produce antibodies that then attack and neutralize foreign invaders, thus preventing infection and disease.

With multiple myeloma, the production of these plasma cells goes out of control. Unlike normal plasma cells that typically comprise about one percent of the cells in the bone marrow, multiple myeloma cells proliferate so that they comprise 10 percent to 80 percent or more of the cells in the bone marrow. In time, myeloma cells collect primarily in the bone marrow and crowd out normal blood cells. The term multiple myeloma describes a characteristic feature of this cancer; it's found at multiple sites within the bone marrow.