Studies using modern chemotherapy to assess tumor-infiltrating lymphocytes (TILs) have confirmed that TILs are predominantly detected in highly proliferative tumors (TNBC and HER2-positive breast cancers) and that their presence at diagnosis is linked to both disease-free (DFS) and overall survival (OS) following adjuvant chemotherapy in these subtypes [168,169]. This evidence concerns the gene ERBB2 and breast cancer.