MPO and acute lymphoblastic leukemia: Furthermore, the proportion of cases which had an altered phenotype on CD34+/MPO+ cells progressively increased in parallel to the number of aberrant markers observed in maturing/mature neutrophils, from 3/14 cases (21%) to 4/8 patients (50%) and 2/2 cases (100%) for BCP-ALL patients presenting with 1, 2 and ≥ 3 aberrant markers on mature/maturing neutrophils (p = 0.02).