Acute erythroid leukaemia. Light micrograph of blood cells from bone marrow in a case of acute erythroid leukaemia. The cells include dystrophic (degenerated) erythroblasts (nuclei stained dark red), one of which is a megaloblast (centre, enlarged erythroblast) with threefold nuclei. Erythroblasts are the immediate precursors to mature red blood cells as they develop from stem cells in the bone marrow. Acute erythroid leukaemia is a rare form of acute myeloid leukaemia (a blood cell cancer) where the excess blood cell production is of erythroblasts. The pale orange cells are normal red blood cells.