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.

Plasma cell neoplasms are diseases in which abnormal plasma 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:

• Lymphoplasmacytic lymphoma (also called Waldenström macroglobulinemia). For more information, see Non-Hodgkin Lymphoma Treatment.
• Plasmacytoma.
• 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, or cause problems with the kidneys, heart, or nerves. MGUS can also become cancer, such as multiple myeloma, lymphoplasmacytic lymphoma, or chronic lymphocytic leukemia.

Plasmacytoma

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.

Signs and symptoms depend on where the tumor is.

• In bone, the plasmacytoma may cause pain or broken bones.
• In soft tissue, the tumor may press on nearby areas and cause pain or other problems. For example, a plasmacytoma in the throat can make it hard to swallow.

Multiple myeloma

In multiple myeloma, abnormal plasma cells (myeloma 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. The myeloma cells also damage and weaken the bone.

Sometimes multiple myeloma does not cause any signs or symptoms. This is called smoldering multiple myeloma. It may be found when a blood or urine test is done for another condition. Signs and symptoms may be caused by multiple myeloma or other conditions. Check with your doctor if you have any of the following:

• Bone pain, especially in the back or ribs.
• Bones that break easily.
• Fever for no known reason or frequent infections.
• Easy bruising or bleeding.
• Trouble breathing.
• Weakness of the arms or legs.
• Feeling very tired.

A tumor can damage the bone and cause hypercalcemia (too much calcium in the blood). This can affect many organs in the body, including the kidneys, nerves, heart, muscles, and digestive tract, and cause serious health problems.

Hypercalcemia may cause the following signs and symptoms:

• Loss of appetite.
• Nausea or vomiting.
• Feeling thirsty.
• Frequent urination.
• Constipation.
• Feeling very tired.
• Muscle weakness.
• Restlessness.
• Confusion or trouble thinking.

Multiple myeloma and other plasma cell neoplasms may cause a condition called amyloidosis.

In rare cases, multiple myeloma can cause peripheral nerves (nerves that are not in the brain or spinal cord) and organs to fail. This may be caused by a condition called amyloidosis. Antibody proteins build up and 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 work the way they should.

Amyloidosis may cause the following signs and symptoms:

• Feeling very tired.
• Purple spots on the skin.
• Enlarged tongue.
• Diarrhea.
• Swelling caused by fluid in your body's tissues.
• Tingling or numbness in your legs and feet.

Age can affect the risk of plasma cell neoplasms.

Anything that increases a person's chance of getting a disease is called a risk factor. Not every person with one or more of these risk factors will develop plasma cell neoplasms, and they will develop in people who don't have any known risk factors. Talk with your doctor if you think you may be at risk.

Plasma cell neoplasms are most common in people who are middle aged or older. For multiple myeloma and plasmacytoma, other risk factors include the following:

• Being Black.
• Being male.
• Having a personal history of MGUS or plasmacytoma.
• Being exposed to radiation or certain chemicals.

Studies about how racial, social, and financial factors affect access to treatment and rates of plasma cell neoplasms are ongoing.

Tests that examine the blood, bone marrow, and urine are used to diagnose multiple myeloma and other plasma cell neoplasms.

In addition to asking about your personal and family health history and doing a physical exam, your doctor may perform the following tests and procedures:

• Blood and urine immunoglobulin studies: A procedure in which a blood or urine sample is checked to measure the amounts of certain antibodies (immunoglobulins). For multiple myeloma, beta-2-microglobulin, M protein, free light chains, and other proteins made by the myeloma cells are measured. A higher-than-normal amount of these substances can be a sign of disease.
• Bone marrow aspiration and biopsy: The removal of bone marrow, blood, and a small piece of bone by inserting a hollow needle into the hipbone or breastbone. A pathologist views the bone marrow, blood, and bone under a microscope to look for abnormal cells. The following tests may be done on the sample of tissue removed during the bone marrow aspiration and biopsy:
  • Cytogenetic analysis: A laboratory test in which the chromosomes of cells in a sample of bone marrow are counted and checked for any changes, such as broken, missing, rearranged, or extra chromosomes. Changes in certain chromosomes may be a sign of cancer. Cytogenetic analysis is used to help diagnose cancer, plan treatment, or find out how well treatment is working.
  • FISH (fluorescence in situ hybridization): A laboratory test used to look at and count genes or chromosomes in cells and tissues. Pieces of DNA that contain fluorescent dyes are made in the laboratory and added to a sample of a patient’s cells or tissues. When these dyed pieces of DNA attach to certain genes or areas of chromosomes in the sample, they light up when viewed under a fluorescent microscope. The FISH test is used to help diagnose cancer and help plan treatment.
  • Flow cytometry: A laboratory test that measures the number of cells in a sample, the percentage of live cells in a sample, and certain characteristics of the cells, such as size, shape, and the presence of tumor (or other) markers on the cell surface. The cells from a sample of a patient's bone marrow are stained with a fluorescent dye, placed in a fluid, and then passed one at a time through a beam of light. The test results are based on how the cells that were stained with the fluorescent dye react to the beam of light. This test is used to help diagnose and manage certain types of cancers, such as leukemia and lymphoma.
• Skeletal bone survey: In a skeletal bone survey, x-rays of all the bones in the body are taken. The x-rays are used to find areas where the bone is damaged. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
• Complete blood count (CBC) with differential: A procedure in which a sample of blood is drawn and checked for the following:
  • The number of red blood cells and platelets.
  • The number and type of white blood cells.
  • The amount of hemoglobin (the protein that carries oxygen) in the red blood cells.
  • The portion of the blood sample made up of red blood cells.
• Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances, such as calcium or albumin, released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease.
• Twenty-four-hour urine test: A test in which urine is collected for 24 hours to measure the amounts of certain substances. An unusual (higher or lower than normal) amount of a substance can be a sign of disease in the organ or tissue that makes it. A higher than normal amount of protein may be a sign of multiple myeloma.
• MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI). An MRI of the spine and pelvis may be used to find areas where the bone is damaged.
• PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.
• CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, such as the spine, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
• PET-CT scan: A procedure that combines the pictures from a positron emission tomography (PET) scan and a computed tomography (CT) scan. The PET and CT scans are done at the same time with the same machine. The combined scans give more detailed pictures of areas inside the body, such as the spine, than either scan gives by itself.

Certain factors affect prognosis (chance of recovery) and treatment options.

The prognosis depends on the following:

• The type of plasma cell neoplasm.
• The stage of the disease.
• Whether a certain immunoglobulin (antibody) is present.
• Whether there are certain genetic changes.
• Whether the kidney is damaged.
• Whether the cancer responds to initial treatment or recurs (comes back).

Treatment options depend on the following:

• The type of plasma cell neoplasm.
• The age and general health of the patient.
• Whether there are signs, symptoms, or health problems, such as kidney failure or infection, related to the disease.
• Whether the cancer responds to initial treatment or recurs (comes back).