Leukaemia blood cells. Light micrograph of large numbers of white blood cells (pink) in the blood vessels (white) of a patient with myeloid leukaemia (cancer of the white blood cells). Myeloid leukaemia affects the myeloid tissue (bone marrow), specifically the white blood cell precursors (myeloblasts) that form a type of white blood cell known as granulocytes. The immature cells fill up the bone marrow and can spill over into the bloodstream and circulate around the body. They do not work properly to fight infection and the underproduction of red blood cells can cause anaemia and fatigue.