CD274 and small cell lung carcinoma: Immunotherapy with pembrolizumab, a humanized immunoglobulin (Ig) G4 (IgG4) antibody targeting programmed death 1 (PD-1) receptors, demonstrated a durable response (overall response rate (ORR) 33%) in PD-L1-expressing SCLC tumors, even in patients with pretreated SCLC [6].