Leukemia (Overview)

What Is It?

Leukemia is a form of cancer that affects the body's ability to make healthy blood cells. It starts in the bone marrow, the soft center of various bones. This is where new blood cells are made. Blood cells include

• Red blood cells, which carry oxygen from the lungs to the body's tissues and take carbon dioxide to the lungs to be exhaled
• Platelets, which help blood clot
• White blood cells, which help fight infections, viruses, and diseases.

Although cancer can affect red blood cells and platelets, leukemia generally refers to cancer of the white blood cells. The disease usually affects one of the two major types of white blood cells: lymphocytes and granulocytes. These cells circulate throughout the body to help the immune system fight off viruses, infections, and other invading organisms. Leukemias arising from lymphocytes are called lymphocytic leukemias; those from granulocytes are called myeloid, or myelogenous, leukemias.