Leukemia is a cancer of the white blood cells. This type of cancer starts in the bone marrow but can then spread to the blood, lymph nodes, the spleen, liver, central nervous system and other organs. In contrast, other types of cancer can start in these organs and then spread to the bone marrow (or elsewhere). Those cancers are not leukemia. Both children and adults can develop leukemia.

Leukemia is a complex disease with many different types and sub-types. The kind of treatment given and the outlook for the child with leukemia vary greatly according to the exact type and other, individual factors.

While both children and adults can develop leukemia, the purpose of this article is to provide an overview of the different types of childhood leukemia: how they develop, whom they affect, and how they are treated. More detailed information about childhood leukemia is available from the American Cancer Society.