With respect to the significance of IL5‐dependent STAT5 activation for differentiation toward eosinophils in normal hematopoiesis, we speculate that multiple pathways other than STAT5, including STAT1, STAT3, MAPK, AKT, and NF‐κB, are critical participants for CEL development and progression. This evidence concerns the gene STAT1 and Chronic Eosinophilic Leukemia, Not Otherwise Specified.