What is it?

Leukemia is a broad term for cancers of the blood cells. Leukemia usually involves the white blood cells which are part of the immune system and are produced and mature in the bone marrow and the lymphatic system. In a state of leukemia, the rate of production of these cells goes out of control, resulting in a very large amount of abnormal white blood cells that do not function properly. The type of leukemia depends on the type of blood cell that becomes cancerous and whether it grows quickly or slowly. Leukemia derived from lymphocyte white cells is lymphocytic leukemia, in contrast to myeloid leukemia which originates from myeloid cells (myeloid white blood cells, red blood cells and platelets). Rapidly progressing leukemia is called acute leukemia, as opposed to chronic leukemia which develops significantly slower. The treatment of leukemia depends very much on its type according to this classification.
Leukemia occurs most often in adults older than 55, but it is also the most common cancer in children younger than 15.