Therapy-related acute myeloid leukemia/myelodysplasia with balanced 21q22 translocations.

The morphologic and immunophenotypic findings of 36 cases of 21q22 acute myeloid leukemia (AML) and myelodysplasia (MDS) were compared, including 14 de novo t(8;21) AMLs, 11 t(8;21) therapy-related AML/MDS cases, and 11 therapy-related AML/MDS cases with other 21q22 balanced translocations [t(n;21)]. Cases were evaluated for the presence of Auer rods, distinct chunky cytoplasmic blast cell granules, promyelocyte increase, cytoplasmic perinuclear clearing (hofs) of blast cells, eosinophil increase, andfeatures of associated trilineage dysplasia. Results of immunophenotyping studies for CD19, CD34, and CD56 expression were compared. Cases of de novo and therapy-related t(8;21) disease shared common morphologic features of chunky cytoplasmic granules, perinuclear hofs, and promyelocyte increases that were not seen consistently in the t(n;21) group of t-AML/MDS cases. Immunophenotypic similarities also were observed between the 2 t(8;21) groups. De novo and therapy-related t(8;21) disease, however, differed by the frequent presence of associated dysplasia in both t-AML/MDS groups, which was infrequent in the de novo t(8;21) group. Therapy-related AMI/MDS with t(8;21) shares characteristic morphologic and immunophenotypic features with de novo t(8;21) AML, but frequently also occurs with associated myelodysplastic changes, similar to other therapy-related acute leukemias.