Leukemia is type of cancer.
Leukemia , also spelled leukaemia , is a group of cancers that usually begin in the bone marrow and result in high numbers of abnormal white blood cells . In children with acute leukemia who are cancer-free after five years , the cancer is unlikely to return . It is the most common type of cancer in children , with three quarters of leukemia cases in children being the acute lymphoblastic type .