Heterogeneity of programmed death-ligand 1 expression and infiltrating lymphocytes in paired resected primary and metastatic non-small cell lung cancer

Multiplex immunofluorescence revealed clear immune differences between primary and metastatic NSCLC. Metastatic lesions showed higher PD-L1, fewer CD8+ T cells, and greater CTL–tumor distances, especially in extrapulmonary or previously treated sites and in EGFR-mutant tumors. These findings highlight the importance of re-evaluating metastatic tissue to guide immunotherapy.