CD4 and breast cancer: There is ample evidence that a pCR in the primary breast cancer following NAC is significantly associated with high levels of tumour infiltration by TILs, CD4+ and CD8+ T effector cells, CD56+ NK cells and high CD8+: FOXP3+ T cell ratios [9, 21, 40, 22, 11, 10, 23, 41, 24–26, 13].