CTLA4 and small cell lung carcinoma: Immune checkpoint inhibitors, including antiprogrammed cell death 1 (PD-1), programmed cell death-ligand 1 (PD-L1), and cytotoxic T lymphocyte-associated protein 4 (CTLA-4) agents, have been widely applied in patients with non-small-cell lung cancer (NSCLC) and small cell lung cancer (SCLC).