CD4 and breast cancer: For effective use of molecular-targeted drugs and immune checkpoint inhibitors involved in intratumor immune responses in the future, more in-depth analyses of differences in the characteristics of immune cells that make up TILs that are present before and after NAC with trastuzumab using biomarkers, such as programmed death 1, programmed death-ligand 1, CD4, CD8, and FOXP3, are needed to evaluate the utility of TILs expression in assessing outcomes in breast cancer patients.