In parallel, the immune microenvironment of early breast lesions, including DCIS, shows prognostic variation in tumor infiltrating lymphocytes (TILs) and checkpoint ligand expression (e.g., PD-L1), supporting the concept that immune contexture and stromal–epithelial interactions influence progression risk and may become biomarkers to tailor preventive interventions [15,72]. Here, CD274 is linked to ductal breast carcinoma in situ.