Leukemia is a cancer of the blood or bone marrow. In Greek, "leukos" means white. Leukemia is characterized by an abnormal overgrowth of blood cells, usually white blood cells known as leukocytes.
Leukemia is divided into 2 forms:
Acute. In acute leukemia, the overgrowth of abnormal immature blood cells occurs rapidly and overcrowds the bone marrow. As a result, the bone marrow is unable to produce healthy normal blood cells. Immediate treatment is required due to the rapid production and accumulation of cancerous cells. These cancerous cells can quickly spill over into the bloodstream and spread to other body organs.
Chronic. In chronic leukemia, the excessive build-up of abnormal blood cells occurs more slowly, taking months to years to progress.
These acute and chronic forms of leukemia are further classified by the type of cells involved:
Lymphoblastic/lymphocytic. This indicates that the cancerous change occurred in a type of immature cell that normally develops into lymphocytes.
Myeloid/myelogenous. This indicates that the cancerous change occurred in a type of immature cell that normally develops into red cells, granulocytes and platelets.
The table below illustrates the four major kinds of leukemia as classified by this system:
It appears likely that a number of risk factors both genetic and environmental contribute to the development of this disease. Possible environmental factors include exposure to radiation, certain chemicals such as benzene and some viruses such as the Epstein-Barr virus.
However, in 95% of leukemia cases, no specific cause can be identified.
The following web sites may provide further helpful information: