Plasma cells are a kind of white blood cell.
In Multiple Myeloma, plasma cells grow rapidly and uncontrollably to form tumors in bone. This interferes with the growth and function of normal cells made by the bone marrow. This cancer occurs mostly in people over 50, and affects African Americans twice as often as White Americans. The most common symptom is bone pain, often in the back or ribs. To evaluate the symptoms, tests are needed to identify the cause.