Significance of cytogenetic abnormalities in acute leukemias.

Chromosome abnormalities of a clonal nature have been found in approximately 50 per cent of the patients with acute nonlymphocytic leukemia and acute lymphocytic leukemia. Patients with acute myeloblastic leukemia (M1 and M2) with only abnormal metaphases have the worst prognosis among patients with acute nonlymphocytic leukemia, whereas patients with acute myeloblastic leukemia (M1 and M2) with only normal metaphases have the best prognosis. Specific abnormalities include a t(8;21) in approximately 8 per cent of the patients with acute nonlymphocytic leukemia and a t(15;17) in approximately 50 per cent of the patients with either hypergranular (M3) or microgranular (M3 variant) promyelocytic leukemia. In patients who develop acute leukemia after cytotoxic or radiation therapy for a previous malignant disease, clonal chromosome abnormalities are almost always present.