CD274 and breast cancer: In breast cancer in general, the correlation between immune cell infiltration and poor prognosis has been well-studied, and has driven investigations into immunotherapy for breast cancer, such as vaccines and strategies targeting tumour-associated macrophages and immune checkpoint pathways such as the PD-1/PD-L1 pathway.60 In postpartum breast cancer patients, additional characterization of the tumor immune microenvironment and its influence on tumor development and progression is needed to address the lack of specific treatment options for this important group of young women.