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Leukemia is a group of cancers that begins in the blood forming cells of the bone marrow.

The term "leukemia" literally means "white blood." White blood cells (leukocytes) are used by the body to fight off infections and other foreign substances. They are made in the bone marrow.

Leukemia leads to an uncontrolled increase in the number of immature white blood cells (or blasts).

Over time, these cancerous blast cells fill up the bone marrow and prevent healthy red cells, platelets, and mature white cells (leukocytes) from being made. Life-threatening symptoms may then develop.

The blast cells spill out of the marrow into the bloodstream and lymph system. They can also travel to the brain and spinal cord (the central nervous system) and other parts of the body.

Leukemias are divided into two major types:

  • Acute (which progresses quickly with many immature white cells)
  • Chronic (which progresses more slowly and has more mature white cells)

For information about a specific type of leukemia, see the following:

For information about leukemia support groups, see: Leukemia resources



Signs and tests

Support Groups

Expectations (prognosis)

Calling your health care provider





Appelbaum FR. The acute leukemias. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 194.

Kantarjian H, O’Brien S. The chronic leukemias. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 195.

Review Date: 3/2/2009
Reviewed By: David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc., and Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital.
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