CD274 and osteosarcoma: The multivariate analysis revealed age (RFS; p = 0.020), M category of stage (OS; p = 0.011), PAK4 positivity (OS; p = 0.028), and PD-L1 positivity (RFS; p = 0.002) as independent indicators of a poor prognosis for the OS or RFS of osteosarcoma patients.