The most obvious characteristic in APL leukemia cells was the positive expression of MPO (+, 100%), CD13 (+, 100%; and homogeneous mean fluorescent intensity (MFI)), CD33 (+, 100%; and homogeneous MFI), CD64 (dim, 100%; and homogeneous MFI), and negative expression of CD11b (0%) and CD10 (0%). The gene discussed is MPO; the disease is acute promyelocytic leukemia.