SEER Logo

SEER Training Modules

Introduction to Leukemia

Leukemias are cancers of the blood-forming tissues. White blood cells may be produced in excessive amounts and are unable to work properly which weakens the immune system.

The blood is made up of fluid called plasma and three types of cells and each type has special functions. White blood cells (also called WBCs or leukocytes) help the body fight infections and other diseases. Red blood cells (also called RBCs or erythrocytes) carry oxygen from the lungs to the body's tissues and take carbon dioxide from the tissues back to the lungs. The red blood cells give blood its color. Platelets (also called thrombocytes) help form blood clots that control bleeding.

Blood cells are formed in the bone marrow, the soft, spongy center of bones. New (immature) blood cells are called blasts. Some blasts stay in the marrow to mature. Some travel to other parts of the body to mature.

Normally, blood cells are produced in an orderly, controlled way, as the body needs them. This process helps keep us healthy. When leukemia develops, the body produces large numbers of abnormal blood cells. In most types of leukemia, the abnormal cells are white blood cells. The leukemia cells usually look different from normal blood cells, and they do not function properly.

Each year, leukemia is diagnosed in about 29,000 adults and 2,000 children in the United States.

In both men and women, leukemia incidence is highest among whites and lowest among Chinese, Japanese, and Koreans. The incidence in men is about 50% higher than in women for all racial/ethnic groups except Vietnamese, among whom the male rates are only slightly higher. Ethnic differences in the incidence rates are small in the youngest adult age group (30-54 years), but become more evident in each of the older age groups. It is found that childhood leukemia rates are highest among Filipinos, followed by white Hispanics, non-Hispanic whites and blacks.