CD274 and breast cancer: Although studies have been conducted to analyze the relationship between PD-L1 and breast cancer, including all subtypes, the prognosis of patients with PD-L1-positive tumors remains controversial: PD-L1 was related to a poor prognosis [19–21], whereas PD-L1 expression was a good prognostic factor for breast cancer [16, 22], especially for basal-like tumors [17].