In the WHO classification of AML (and myeloid neoplasms in general), the chromosomal rearrangements/fusion genes play an important role in the grouping of AMLs into diagnostic-prognostic-therapeutic entities; for example, rearrangements such as t(8;21)(q22;q22) (fusion gene RUNX1-RUNX1T1), inv(16)(p13.1q22) (fusion gene CBFB-MYH11), and t(15;17)(q22;q12) (fusion gene PML-RARA) define specific AML subsets and their finding is sufficient for an AML diagnosis regardless of the blast percentage in the blood or bone marrow [1]. The gene discussed is RARA; the disease is acute myeloid leukemia.