Compared with lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), SCLC exhibits a markedly lower infiltration of CD8+ T cells [18], which may partly stem from reduced expression of the chemokine CCL5—a critical mediator of immune cell recruitment to the tumor microenvironment [19, 20]. This evidence concerns the gene CD8A and small cell lung carcinoma.