CD34 and Ewing sarcoma: In the case of Ewing sarcoma, as already mentioned in Section 2.1.2, Luo et al. developed an orthotopic humanized mouse model of Ewing sarcoma, by transplanting fresh human cord blood CD34+ HSC into NSG-SGM3 mice combined with subsequent Ewing sarcoma patient-derived cell engraftment in the tibia of the humanized mice [67].