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:
For information about a specific type of leukemia, see the following:
For information about leukemia support groups, see: Leukemia resources