ERBB2 and breast cancer: The results verified the variation in PD-L1 expression across diverse BC patients' molecular subtypes as both luminal B, and TNBC demonstrated significant upregulation of PD-L1 (p = 0.0044 and p < 0.0001, respectively), in contrast to luminal A who displayed a significant downregulation of PD-L1 (p = 0.0181), in addition to a non-significant expression of PD-L1 in HER2/luminal B and HER2/neu compared to controls.