Cytogenetics are main predictors of outcome in patients with MDS and AML. In fact, a monosomy 5 (-5) or del5q (excluding typical 5q-syndrome) are mostly poor prognostic markers also because being frequently part of a complex karyotype. Together, these patients often do not respond to conventional chemotherapy and can only be cured by allogeneic HSCT. Nevertheless, even after transplantation the relapse rate is considerably high and in the majority of patient's relapses occur within the first year after HSCT.