CD33 and acute promyelocytic leukemia: Bone marrow aspiration confirmed relapsed APL (Figures 1A,B), supported by immunophenotypic markers (CD33+, CD117+, cMPO+, HLA-DR−, CD34−), cytogenetic showing 46, XX, t(15,17)(q22;q12) [20 metaphases] (Figure 1D), and molecular evidence of PML-RARα fusion by FISH (Figure 1C).