Multiple Myeloma What is Multiple Myeloma? Multiple myeloma, also known as myeloma, hematologic cancer, or cancer of the blood is a plasma cell cancer, a type of white blood cell made in the bone marrow that is responsible for creating antibodies. A Multiple myeloma diagnosis means a group of these plasma cells has become cancerous and is multiplying. This cancerous multiplication of plasma cells raises the the level of abnormal proteins in circulating blood, and reduces the space available in the