CD274 and breast carcinoma: The association between certain clinicopathological factors and PD-L1 expression in breast cancer has been reported in various studies.17 26 A meta-analysis revealed that PD-L1 expression in breast tumours is a poor prognostic clinicopathological factor, as it is related to lymph node metastasis, poor nuclear grade and negative oestrogen receptor status.27 The present study similarly concluded that PD-L1 expression in tumours correlates with both poor grade and more aggressive tumour subtypes.