From a prognostic perspective, several studies in HER2+ BC patients receiving neoadjuvant (Table 1) or adjuvant [7, 24, 27–30] anti-HER2-based chemotherapy have shown that expression of immune-associated gene signatures and infiltration by TILs in pre-treatment biopsies associated with longer DFS [10], independently of known prognostic clinical-pathological variables. Here, ERBB2 is linked to breast cancer.