Leukaemia is cancer of blood-forming tissues, including bone marrow. Many types exist such as acute lymphoblastic leukaemia, acute myeloid leukaemia and chronic lymphocytic leukaemia.Many patients with slow-growing types of leukaemia don't have symptoms. Rapidly growing types of leukaemia may cause symptoms that include fatigue, weight loss, frequent infections and easy bleeding or bruising.Treatment is highly variable. For slow-growing leukaemias, treatment may include monitoring. For aggressive leukaemias, treatment includes chemotherapy that's sometimes followed by radiation and stem-cell transplant. Blood cancers affect blood cells and bone marrow -- the spongy tissue inside your bones where blood cells are made. These cancers change the way blood cells behave and how well they work.