Acute myeloid leukaemia. Light micrograph of blood cells from bone marrow in a case of acute myeloid leukaemia. These cells include hemocytoblasts (hematopoietic stem cells). Leukaemia is a cancer where certain blood cells form in excess. There are several acute forms, classified according to the type of cell affected. Acute myeloid leukaemia is a cancer affecting the myeloid tissue (bone marrow), specifically the white blood cell precursors (myeloblasts) that form a type of white blood cell known as granulocytes.