MPO and acute myeloid leukemia: At presentation, he had significant leukocytosis of 40.0 K/mm3, and flow cytometry of peripheral blood reported a prominent (55%) blast population characterized by the expression of CD34, CD117 (partial), CD13, CD33, CD123, HLA-DR, CD38, TdT, CD7, and minimal expression of myeloperoxidase (MPO), with negativity for B-cell and other T-cell markers, immunophenotypically consistent with AML.