Endothelial cells with high endomucin expression have previously been reported to colocalize with osteoblast progenitors in the growth plate regions of the femoral bone and are responsible for hematopoietic stem cell (HSC) maintenance by secreting HSC-supporting cytokines.36 These data suggest that ALL transforms the endothelial subset away from a hematopoietic supporting niche in support of ALL. Here, EMCN is linked to acute lymphoblastic leukemia.