PDCD1 and non-small cell lung carcinoma: One study found that PD-L1 expression was less common in primary NSCLC tumor samples compared with metastases measured both in histologic and cytological cohorts.[31] These data suggest that assessing PD-L1 expression in freshly collected tissue and from metastatic sites before treatment with anti-PD-1/PD-L1 agents is important.