Donor cell-derived hematological malignancies after allogeneic hematopoietic stem cell transplantation

Donor cell-derived leukemia/lymphoma (DCL) is an extremely rare outcome after allogeneic hematopoietic stem cell transplantation (allo-SCT). Owing to the rarity of DCL, most available data have been limited to case reports or small case series. Two previous large surveys assessed the frequency of DCL; the European Group for Blood and Marrow Transplantation identified 14 DCL cases from 10,489 allo-SCTs, and the University of Minnesota reported eight cases from 2,390 engrafted allo-SCTs. Recently, a Japanese survey identified 40 DCL cases from 36,870 allo-SCTs, and the incidence of DCL was estimated as 0.16% at 15 years. Through these analyses, cord blood was considered as a risk factor for DCL development compared to other stem cell sources, and it should also be noted that donor age was positively correlated with DCL incidence. Further molecular and immunological investigations would clarify the pathogenesis of DCL and may provide additional clues for understanding the underlying mechanisms of typical hematological malignancies.