CTLA4 and small cell lung carcinoma: Recently, immune checkpoint inhibitors (ICIs), which modulate the immune system by targeting immune checkpoints, such as programmed cell death protein 1 (PD-1) [12,13], programmed cell death ligand 1 (PD-L1) [14], and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) [15], have been enrolled in the standard of care for both NSCLC and SCLC [14,16].