CD34 and chronic myelogenous leukemia, BCR-ABL1 positive: To determine the basis of this heterogeneity, we conducted the first exhaustive characterization of the DNA methylation pattern of sorted CP‐CML CD34+CD15− (immature) and CD34−CD15+ (mature) cells at diagnosis (prior to any treatment) and compared it to that of CD34+CD15− and CD34−CD15+ cells isolated from healthy donors (HD).