Leukemia (American English) or leukaemia (British English) (from the Greek leukos Î»ÎµÏÎºÎ¿Ï‚ - white, and haima Î±Î¯Î¼Î± - blood) is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases. In turn, it is part of the even broader group of diseases affecting the blood, bone marrow and lymphoid system, which are all known as hematological neoplasms.
In 2000, approximately 256,000 children and adults around the world developed some form of leukemia, and 209,000 died from it. About 90% of all leukemias are diagnosed in adults.[not in citation given]