PDCD1 and breast carcinoma: Interestingly, when comparing the immune microenvironment in different PAM50 subtypes, ER− patients had the most Tregs, PD-L1+ TAMs, and PD-1 high CTLA-4+ CD38+ exhausted T cells, revealing that breast cancer microenvironment is remodeled by the endocrine system to promote immunosuppressive function.