Although fibroblastic osteosarcoma specimen OS-7 did not exhibit the readily discernable spatial differences in CXCR4, CXCL12, and MIF expression observed in the other specimens (Figure 8A), ligand-receptor analysis did indeed provide evidence of regional differences in the CXCR4 signaling axis (Figure 8B). This evidence concerns the gene CXCL12 and osteosarcoma.