Several in vitro studies on NB cell lines suggested a pivotal role of the CXCL12-CXCR4 axis in BM infiltration [3–6], but the demonstrations that CXCR4 is not functional in BM-infiltrating NB cells [7], and that BM resident cells in NB patients have significantly lower expression of CXCL12 than in healthy children [8], do not support a role for this axis in stage M NB patients. This evidence concerns the gene CXCL12 and neuroblastoma.