CD274 and chondrosarcoma: If this association is corroborated by additional results and reflects a cause effect relationship, then one potential mechanism for the metastatic spreading is the escape of tumor cells from immunosurveillance because of T cell exhaustion caused by the inhibitory signals triggered by the interactions between PD-1 expressed on T cells and PD-L1 expressed on chondrosarcoma cells and macrophages in the tumor microenvironment.