CD274 and metastatic neoplasm: PD-L1 expression is the earliest and most widely used predictive biomarker for PD-1/PD-L1 inhibitors (6), but it is limited by the detection technology employed (multiple detection antibodies, instrument platforms, different thresholds for positivity) and histological sources of PD-L1 (immune and tumor cells, primary and metastatic tumor sites, and dynamic changes in PD-L1 after treatment) (7).