CD274 and triple-negative breast carcinoma: Despite significantly improved progression-free survival (PFS) with pembrolizumab-chemotherapy in PD-L1-positive (CPS ≥10) previously untreated locally recurrent inoperable or metastatic triple-negative breast cancer (median PFS 9.7 vs. 5.6 months; HR 0.65), deep responses remain limited—highlighting persistent therapeutic challenges (15).