Clinically and molecularly, therapy-related acute myeloid leukemia (t-AML) and therapy-related myelodysplastic syndrome (t-MDS) are distinct entities, but both are characterized by the frequent rearrangement of chromosomes 5 and 7, an increased incidence of TP53 mutation, and high rates of resistance to chemotherapy (11). The gene discussed is TP53; the disease is myelodysplastic syndrome.