CD33 and acute promyelocytic leukemia: Multiparameter flow cytometry of BM aspirate detected 78% blasts and suggested an immunophenotype that was positive for CD13, CD33, CD117, and MPO, and negative for CD3, CD10, CD11b, CD14, CD15, CD19, CD34, CD71, CD79a, and HLA-DR, corresponding to APL features.