CD4 and breast cancer: The umap plot showed that primary breast cancer was enriched with CD8/CD4+ T cells (28.9 % and 14.3 %), B cells (9.6 %) and CAFs (9.2 %) (Fig. 5A), while breast cancer brain metastasis was enriched with CAFs (21.7 %) and epithelial cells (37.9 %), while CD8+ T cells (3.7 %), CD4+ T cells (1.5 %) and B cells (0.46 %) were significantly decreased (Fig. 5B).