We demonstrated that MUC4 acts as a physical barrier for immune exclusion in TNBC and HER2+ breast cancer, since tumor samples from patients with MUC4+ tumors evidenced scarce or null presence of TILs, while patients with MUC4- tumors evidenced abundant TILs on their TME (31, 124). This evidence concerns the gene MUC4 and breast carcinoma.