Distinct morphological subgroups in French-American-British (FAB) classification associate with different chromosomal rearrangements and acquisition of recurring genetic abnormalities; for example t(8;21))(q22;q22) and t(15;17))(q22;q21) create fusion genes, AML/ETO and PML/RARα, which predominate in FAB M2 and M3 AML subtypes respectively. This evidence concerns the gene RARA and acute myeloid leukemia.