These cells cultured with myeloid cytokines continue to proliferate and differentiate, eventually leading to leukemia.47 A comparison of the genetic landscape of 2 groups of patients with lineage switch categorized based on the presence or absence of KMT2A mutation showed that the latter group had more features of chronic myeloid malignancy, suggesting a pivotal role of KMT2A in breaking the barrier of cell lineage.1 Here, KMT2A is linked to leukemia.