Plasma cell neoplasms are diseases in which the body makes too many plasma cells.
Plasma cells develop from B lymphocytes (B cells), a type of white blood cell that is made in the bone marrow. Normally, when bacteria or viruses enter the body, some of the B cells will change into plasma cells. The plasma cells make antibodies to fight bacteria and viruses, to stop infection and disease.
Blood cell development. A blood stem cell goes through several steps to become a red blood cell, platelet, or white blood cell.
Plasma cell neoplasms are diseases in which abnormal plasma cells or myeloma cells form tumors in the bones or soft tissues of the body. The plasma cells also make an antibody protein, called M protein, that is not needed by the body and does not help fight infection. These antibody proteins build up in the bone marrow and can cause the blood to thicken or can damage the kidneys.
Plasma cell neoplasms can be benign (not cancer) or malignant (cancer).
Monoclonal gammopathy of undetermined significance (MGUS) is not cancer but can become cancer. The following types of plasma cell neoplasms are cancer:
- Waldenström macroglobulinemia. (See Adult Non-Hodgkin Lymphoma Treatment for more information.)
- Multiple myeloma.
There are several types of plasma cell neoplasms.
Plasma cell neoplasms include the following:
Monoclonal gammopathy of undetermined significance (MGUS)
In this type of plasma cell neoplasm, less than 10% of the bone marrow is made up of abnormal plasma cells and there is no cancer. The abnormal plasma cells make M protein, which is sometimes found during a routine blood or urine test. In most patients, the amount of M protein stays the same and there are no signs, symptoms, or health problems. In some patients, MGUS may later become a more serious condition, such as amyloidosis. It can also become cancer, such as multiple myeloma, lymphoma, or chronic lymphocytic leukemia.
In this type of plasma cell neoplasm, the abnormal plasma cells (myeloma cells) are in one place and form one tumor, called a plasmacytoma. Sometimes plasmacytoma can be cured. There are two types of plasmacytoma.
- In isolated plasmacytoma of bone, one plasma cell tumor is found in the bone, less than 10% of the bone marrow is made up of plasma cells, and there are no other signs of cancer. Plasmacytoma of the bone often becomes multiple myeloma.
- In extramedullary plasmacytoma, one plasma cell tumor is found in soft tissue but not in the bone or the bone marrow. Extramedullary plasmacytomas commonly form in tissues of the throat, tonsil, and paranasal sinuses.