Recent work by Rajakumar et al. (2021) used BCR-ABL1 positive, patient-derived BCP-ALL xenotransplanted into the femur of NSG mice to demonstrate that the ALL blasts invaded calvarial and vertebral bone marrow well before being identified in the SAS and that the blasts themselves created channels through RANKL-mediated bone destruction to gain access to the dura mater, arachnoid mater and finally SAS [131]. This evidence concerns the gene TNFSF11 and acute lymphoblastic leukemia.