Acute myeloid leukemia with t(6;9) (p23;q34): association with myelodysplasia, basophilia, and initial CD34 negative immunophenotype

Abstract

The translocation (6;9)(p23;q34) is a rare cytogenetic aberration found in patients with acute myeloid leukemia (AML). The clinical, morphologic, and immunophenotypic findings of eight t(6;9) acute leukemias are described. The patients included six men and two women with a mean age of 38.5 years. The leukemias were classified in the French-American-British (FAB) system as AML FAB M2 in four cases and as FAB M4 in four cases. Underlying myelodysplasia was evident in six cases. Bone marrow basophilia was found at presentation in six of the seven cases studied. In two cases with basophilia, darkly stained granules were also present in many eosinophils. In one case, initial basophilia was absent, but was present at relapse, as were eosinophils containing darkly stained granules. Iron stains were available in five cases; four showed increased incorporation and three had ringed sideroblasts. All cases studied by flow cytometry (six at presentation and three at relapse) expressed CD13, CD33, and human leukocyte antigen-DR. At presentation, five cases were CD34 negative. In one case at presentation, a subset of blasts (18%) weakly expressed CD34. Three cases studied at relapse were positive for CD34. Two of seven cases studied were terminal deoxynucleotidyl transferase positive. The t(6;9)(p23;q34) was the only cytogenetic abnormality in five cases. Trisomy 8 was found in two cases, and ring 12 was present in one case. Three patients are living with refractory leukemia 6 weeks to 6 months after initial diagnosis, and three patients died of complications of allogeneic bone marrow transplantation. Only one patient is alive without evidence of disease 3 years after bone marrow transplantation. t(6;9) leukemia is an unusual type of AML that is associated with poor prognosis, early age of onset, basophilia, myelodysplasia with frequent ringed sideroblasts, and a CD34-negative initial phenotype.