ERBB2 and breast cancer: CD8+ CTLs indicative of anti-tumor immune responses, as well as FOXP3+ Treg cells indicative of a tumorigenic immune response, were most prominent in TNBC (60% infiltrated with CTLs and 70% infiltrated with Treg) and HER2+ (61% and 67%) tumors compared to HR+ breast cancers (43% and 38%) [36].