CD33 and acute promyelocytic leukemia: Nevertheless, conventional morphology, which can detect the presence of atypical promyelocytes with numerous, bright azurophilic granules, and intracellular inclusions organized in faggots or bundles (Auer rods) on the peripheral blood and bone marrow aspirate smears, as well as multiparametric flow-cytometry, which highlights high side scatter, positivity for CD13, CD33, CD117, and MPO, and negativity for CD34 and HLA-DR, remain essential tools in APL diagnosis, with cytomorphology being the cheapest and widely available laboratory technique [2,6,8,9,10].