July 27, 2017

Plasma Cell Neoplasm — A Brief Primer

While multiple myeloma is the primary disease treated at the Myeloma Center, other plasma cell neoplasms are also the focus of our research and treatment regimens.

What is a Plasma Cell Neoplasm?

A neoplasm is an abnormal mass of tissue that results when cells divide more than they should or do not die when they should.

A plasma cell neoplasm is a disease 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 change into plasma cells. The plasma cells make antibodies to fight bacteria and viruses and to stop infection and disease.

In plasma cell neoplasms, the abnormal plasma cells form tumors in the bones or soft tissues of the body. The plasma cells also make an antibody protein (M protein) that is not needed by the body and does not help fight infection. These antibody proteins can cause the blood to thicken or can damage the kidneys.

Neoplasms and plasma cell neoplasms can be benign (not cancer) or malignant (cancer).

Monoclonal gammopathy of undetermined significance (MGUS) is a benign plasma cell neoplasm.  Malignant plasma cell neoplasms include plasmacytoma, multiple myeloma, Waldenstrom macroglobulinemia and amyloidosis.

Monoclonal Gammopathy of Undetermined Significance (MGUS)

In MGUS, less than 10 percent of the bone marrow is made up of abnormal plasma cells. 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 symptoms or health problems.

In some patients, MGUS may later become a more serious condition, such as amyloidosis, or cause problems with the kidneys, heart or nerves. MGUS can also become multiple myeloma, Waldenstrom macroglobulinemia or chronic lymphocytic leukemia.


A plasmacytoma forms when the abnormal plasma cells are in one place and form one tumor. There are two types of plasmacytoma.

In an isolated plasmacytoma of bone, one plasma cell tumor is found in the bone. Less than 10 percent of the bone marrow is made up of plasma cells and there are no other signs of cancer. Over time, 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.

Plasmacytoma of bone can cause pain or broken bones. In soft tissue, the tumor may press on nearby areas and cause pain or other problems (for example, difficulty swallowing).

Multiple Myeloma

In multiple myeloma, abnormal plasma cells build up in the bone marrow and form tumors in many bones of the body. These tumors may keep the bone marrow from making enough healthy blood cells. Normally, the bone marrow makes stem cells — immature cells — that become three types of mature blood cells:

Red blood cells that carry oxygen and other substances to all tissues of the body

White blood cells that fight infection and disease

Platelets that form blood clots to help prevent bleeding

As the number of myeloma cells increases, fewer red blood cells, white blood cells and platelets are made. In addition, the myeloma cells can damage and weaken the bone and cause hypercalcemia (too much calcium in the blood), which can cause confusion and damage organs.

Sometimes multiple myeloma does not cause any signs or symptoms. This is called smoldering multiple myeloma. Smoldering multiple myeloma needs close monitoring since it can become multiple myeloma.

Waldenstrom Macroglobulinemia

In Waldenstrom macroglobulinemia, abnormal plasma cells build up in the bone marrow, lymph nodes and spleen. They make too much M protein, which causes the blood to become thick. The lymph nodes, liver and spleen may become swollen. The thickened blood may cause problems with blood flow in small blood vessels.


Multiple myeloma and other plasma cell neoplasms may cause amyloidosis. Amyloidosis occurs when antibody proteins stick together in peripheral nerves and organs such as the kidney and heart.  This can cause the nerves and organs to become stiff and unable to function properly.

Related Conditions

POEMS Syndrome

POEMS syndrome (Polyneuropathy, Organomegaly, Endocrinopathy, Monoclonal gammopathy, Skin changes) is a rare, multi system condition associated with plasma cell neoplasms. It is characterized by overproduction of plasma cells, which can cause damage to the nerves, liver and spleen, diabetes or thyroid problems, and skin rashes.

Castleman Disease

Castleman disease is a rare disease of the lymph nodes and related tissues that results from the overgrowth of benign cells in the body’s lymphatic system (the tissues and organs that produce, store and carry white blood cells that fight infections and other diseases).

In unicentric Castleman disease, only one group of lymph nodes in one part of the body — usually the chest or abdomen — is affected.

In multicentric Castleman disease, many groups of lymph nodes and lymphoid tissue throughout the body are affected and the immune system is weakened. Castleman disease involving plasma cells tends to be multicentric. Patients with multicentric Castleman disease are at increased risk of developing lymphoma.

Source: National Cancer Institute