The French-American-British classification of 1976 clearly recognized APL (M3 type) and its peculiar morphologic features: these included marrow infiltration by dysplastic promyelocytes with heavy granulations and sometimes bundles of Auer rods ("faggots") accompanied by a strong myeloperoxidase (MPO) staining in the cytoplasm.11 Few years later, a microgranular variant (M3v) of the disease was identified and recognized in the updated FAB classification.12 This variant accounts for 20% of cases approximately. Here, MPO is linked to acute promyelocytic leukemia.