Immunophenotypic features of APL, bone marrow aspirate. Side scatter (SS) is plotted against antigen expression. Cyan, blast cells; magenta, lymphocytes. There are no monocytes or granulocytes in this diagnostic sample. The blast cells mimic the position of neutrophils but lack CD15 (and CD16 and CD11b, not shown). They express CD117 together with CD13 and CD33 but lack CD34 and HLA-DR. They also strongly express MPO.