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What Is Multiple Myeloma?
Normal Blood Cells
Myeloma Cells
Multiple myeloma is
cancer
that begins in
plasma cells,
a type of
white blood cell.
To understand multiple myeloma, it is helpful to know about normal blood
cells.
Most blood cells develop from cells in the
bone marrow
called
stem cells. Bone
marrow is the soft material in the center of most bones.
Stem cells mature into different types of blood cells. Each type has a special
function:
-
White blood cells help fight
infection.
There are several types of white blood
cells.
-
Red blood cells
carry oxygen to
tissues
throughout the body.
-
Platelets
help form blood clots that control bleeding.
Plasma cells are white blood cells that make
antibodies.
Antibodies are part of
the
immune system.
They work with other parts of the immune system to help
protect the body from germs and other harmful substances. Each type of plasma
cell makes a different antibody.
Normal plasma cells help protect the body from germs and other harmful
substances.
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Myeloma, like other cancers, begins in cells. Normally, cells grow and divide
to form new cells as the body needs them. When cells grow old, they die, and
new cells take their place. In cancer, this orderly process goes wrong. New
cells form when the body does not need them, and old cells do not die when they
should. These extra cells can form a mass of tissue called a growth or
tumor.
Myeloma begins when a plasma cell becomes
abnormal. The abnormal cell divides
to make copies of itself. The new cells divide again and again, making more and
more abnormal cells. The abnormal plasma cells are myeloma cells. Myeloma cells
make antibodies called
M proteins.
In time, myeloma cells collect in the bone marrow. They may crowd out normal
blood cells. Myeloma cells also collect in the solid part of the bone. The
disease is called "multiple myeloma" because it affects many bones. (If myeloma
cells collect in only one bone, the single mass is called a
plasmacytoma.)
Multiple myeloma is the most common type of
plasma cell tumor. This booklet
does not deal with other kinds of plasma cell tumors. The Cancer Information
Service (1-800-4-CANCER) can send information about those diseases.
Myeloma cell (abnormal plasma cell) making M proteins.
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Multiple myeloma is not bone cancer. Although multiple myeloma affects the
bones, it begins in blood cells, not bone cells.
Bone cancer is a different disease. It begins in bone cells, not blood cells.
Bone cancer is diagnosed and treated differently from multiple myeloma.
The NCI's fact sheet "Bone Cancer: Questions and Answers" provides information
about bone cancer. This fact sheet and other materials are available from the
Cancer Information Service (1-800-4-CANCER) and on NCI's Web site
(http://www.cancer.gov).
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