CD274 and breast cancer: This leads us to investigate the prognostic role of PD-L1 in ER negative disease as a whole with the novel finding that high PD-L1 is significantly associated with improved RFS and OS in this subset of breast cancer (HR 0.36 (95%CI 0.195-0.761) p=0.0063 and 0.154 (95%CI 0.103-0.526) p=0.0005, respectively) (Figure 6(h) and Supp Fig3G).