THE WORD LEUKEMIA literally means white blood. Leukemia is the term used to describe cancer of the blood-forming tissues known as bone marrow. This spongy material fills the bones in the body and produces healthy blood cells. The bone marrow of children with cancer creates millions of cancerous white cells, which have lost the ability to stop multiplying. As the bone marrow becomes packed with these malignant cells, they crowd out all the healthy cells the blood needs to do its work and symptoms of leukemia begin to develop.

This chapter provides an overview of childhood leukemia. Because leukemia is a disease of the blood cells, it first looks at the function and composition of blood. It briefly describes the four types of childhood leukemia and how many children and teens are diagnosed with these diseases. It then explains the genetics of leukemia, because the results of genetic tests help determine diagnosis, treatment, and likely response to treatment. Chapter 3, Acute Lymphoblastic Leukemia; Chapter 4, Acute Myeloid Leukemia; Chapter 5, Juvenile Myelomonocytic Leukemia; and Chapter 6, Chronic Myelogenous Leukemia describe each type of leukemia in detail and the current treatments used.