Due to our much advanced understanding of the adult hematopoietic SCs (HSCs), CSCs were first reported in human acute myeloid leukemia (AML), in which leukemic cells expressing the same markers as normal adult HSCs (CD34+CD38–) were much more efficient at engrafting and propagating the leukemia in immune-deficient mice (Lapidot et al., 1994; Uckun et al., 1995; Doulatov et al., 2012). The gene discussed is CD34; the disease is leukemia.