CTLA4 and breast cancer: As novel therapeutic interventions for BC are on the rise, including immune checkpoint inhibitors targeting Programmed cell Death (PD)-1 receptor and its ligand PD-L1, as well as cytotoxic T-lymphocyte-associated Protein 4 (CTLA4), guiding intervention through the stratification of BC patients according to the risk for relapse and/or to the predicted drug response becomes even more critical in the selection of optimal treatment approach.