PDCD1 and small cell lung carcinoma: Immune checkpoint inhibitors (programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4)) have become standard components in both the first line and subsequent lines of systemic therapy for metastatic NSCLC and SCLC (1, 3).