CD274 and osteosarcoma: The current study indicates that metastatic, but not primary, osteosarcoma tumors express PD-L1 and PD-1 with ~75% positivity rate13,14, whereas some studies exhibit that PD-L1 is detected in primary osteosarcoma with positivity rates of 6.8% and 35.5%, respectively15,16, and no significant differences are observed between primary and metastatic osteosarcoma.