The median tumor-infiltrating lymphocyte (TIL) category in brain metastases was 5% (1%–70%), and the TIL percentage in primary breast tumor tissue and the number of CD4/CD8/Foxp3-positive cells were significantly higher than in brain metastatic breast tumor tissue, especially in patients with triple-negative breast cancer, where reduced TIL number was associated with shorter overall survival [46]. The gene discussed is CD4; the disease is neoplasm.