CD19 and precursor B-cell acute lymphoblastic leukemia: Considering that B-ALL has mostly been reported as a progenitor or precursor hematopoietic cell disease, we decided to analyze the content of precursor (CD34−CD38+), progenitor (CD34+CD38+), or stem (CD34+CD38−) cells in the blastic population (CD19+CD45−/intermediate) by flow cytometry (Figure 2a).