What Is Leukemia?
Normal Blood Cells
Leukemia Cells
Leukemia is cancer that starts in the tissue that
forms blood. To understand cancer, it helps to know
how normal blood cells form.
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 kinds of blood cells.
Each kind has a special job:
White blood cells, red blood cells, and platelets are
made from stem cells as the body needs them. When
cells grow old or get damaged, they die, and new cells
take their place.
The picture below shows how stem cells can mature
into different types of white blood cells. First, a stem
cell matures into either a myeloid stem cell or a
lymphoid stem cell:
- A myeloid stem cell matures into a myeloid blast.
The blast can form a red blood cell, platelets, or one
of several types of white blood cells.
- A lymphoid stem cell matures into a lymphoid blast.
The blast can form one of several types of white
blood cells, such as B cells or T cells.
The white blood cells that form from myeloid blasts
are different from the white blood cells that form from
lymphoid blasts.
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Picture of blood cells maturing from stem cells. |
Most blood cells mature in the bone marrow and
then move into the blood vessels. Blood flowing
through the blood vessels and heart is called the
peripheral blood.
In a person with leukemia, the bone marrow makes
abnormal white blood cells. The abnormal cells are
leukemia cells.
Unlike normal blood cells, leukemia cells don't die
when they should. They may crowd out normal white
blood cells, red blood cells, and platelets. This makes it
hard for normal blood cells to do their work.
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