Fig. 2

Immunohistochemical analysis (original magnification × 200). a CD4+ lymphocytes. b CD8+ lymphocytes. c CTLA4– lymphocytes. d CD68+ cells. e Glial fibrillary acid protein (GFAP) weak positive-reactive astrocytes. f GFAP moderate positive-reactive astrocytes. g Programmed cell death protein 1 receptor (PD-1)-negative expression on stromal tumor infiltrating lymphocytes (TILs) in the brain microenvironment. h PD-1-positive expression on TILs in the brain microenvironment. i PD-L1 negative expression on TILs in brain microenvironment. j Programmed cell death protein 1 receptor ligand (PD-L1)-negative expression in breast cancer brain metastases (BCBM). k PD-L1 weak positive expression in BCBM. l PD-L1 moderate positive expression in BCBM. m PD-L2 negative expression in TILs in the brain microenvironment. n PD-L2 negative expression in BCBM. o PD-L2 weak positive expression in BCBM. p PD-L2 moderate positive expression in BCBM