Indeed, recent studies on SCLC biology showed a low expression of PD-L1 and tumour-infiltrating lymphocytes (TILs) in SCLC samples in contrast to a higher expression of other immune inhibitory proteins, such as B7-H3, the T cell immunoreceptor with immunoglobulin and ITIM domain (TIGIT), the T cell immunoglobulin mucin receptor 3 (TIM3), the lymphocyte activation gene 3 (LAG3), and others [149, 150]. This evidence concerns the gene CD274 and small cell lung carcinoma.