CD274 and non-small cell lung carcinoma: Unlike other biomarkers in NSCLC, PD-L1 protein expression does not give a binary signal, instead, it presents as a continuum of expression including absent, low, medium, and high levels, and also varies between tumor cells [55]; some tumors classified as PD-L1 low/negative at the biopsy site may be PD-L1 high at a different location.