Definition of Leukemia:

Leukemia is a type of blood cancer that begins in the bone marrow. Bone marrow is the soft tissue in the center of the bones, where blood cells grow.

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 white blood cells.

The cancerous cells prevent healthy red cells, platelets, and mature white cells (leukocytes) from being made. Life-threatening symptoms may then develop.

The cancer cells spread to the bloodstream and lymph nodes. 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)
• Chronic (which progresses more slowly)

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

• Acute lymphocytic leukemia (ALL)
• Acute myelogenous leukemia (AML)
• Chronic lymphocytic leukemia (CLL)
• Chronic myelogenous leukemia (CML)
• Hairy cell leukemia

For information about leukemia support groups, see: Leukemia resources