CD274 and breast carcinoma: It has been reported that PD‐L1 expression in tumor tissue might lead to T‐cell exhaustion and unresponsiveness (Berghoff et al., 2015; Crespo et al., 2013), and this was correlated with poor prognosis in many solid tumors such as esophageal cancer (Ohigashi et al., 2005), breast cancer (Ghebeh et al., 2006), renal cancer (Thompson et al., 2006) and melanoma (Hino et al., 2010).