T lymphocytes, especially the CD8+ subset, function as the main “executioners” in the anti‐tumor immune response.[23] We therefore assessed infiltration by T cells and CD8+ T lymphocytes by performing a retrospective analysis of CD3 and CD8α expression in the cancer tissues of patients from the Second Hospital of Dalian Medical University who had lung cancer brain metastases (LCBM) or primary lung cancer (PLC). The gene discussed is CD8A; the disease is lung carcinoma.