ERBB2 and breast cancer: However, the majority of breast cancer tumours do not display elevated numbers of TILs, with the median percentage of stromal TILs reported as 10% in ER+ breast cancer, 15% in HER2+ breast cancer and 20% in TNBC, whereas the median intratumoral infiltration drops to 1.5, 3 and 5%, respectively (Loi et al. 2013b), thus limiting the therapeutic benefit of these approaches.