CD34 and acute promyelocytic leukemia: Kikushige et al. reported that Tim-3 was expressed in the leukemic stem cell fraction (Lin–CD34+CD38–) and common progenitor fraction (Lin–CD34+CD38+) in AML patients, except for those with acute promyelocytic leukemia, while Tim-3 was undetectable on normal hematopoietic stem cells [21].