CD274 and small cell lung carcinoma: The wide use of immune checkpoint inhibitors (ICIs) has paved the road for a novel age of oncology therapeutics, which could block the programmed cell death 1 (PD-1), programmed death-ligand 1(PD-L1), and cytotoxic T lymphocyte-associated protein 4 (CTLA-4) signaling pathways, and are becoming a novel treatment for ES-SCLC since such schemes could enhance survival rate and quality-of-life.