CD274 and cancer: To predict a response to immunotherapy, testing for programmed death-ligand 1 (PD-L1) expression, microsatellite instability (MSI), and tumor mutational burden (TMB) can be useful, but status is not yet clear for most cancer entities.<h4>Methods</h4>Single case study and review of the literature.<h4>Case presentation</h4>This report presents the case of a 37-year-old patient with metastatic advanced osteosarcoma, who had no more established options for tumor treatment left.