ESR1 and neoplasm: In this study, positive staining (both membranous and cytoplasmic) for PD-L1 was observed in 152 out of 650 BC patients, and a significant correlation was observed between PDL-1 positivity and several clinicopathological parameters (large tumor size, lymph node involvement, tumor grade, ER negativity, HER2-positive tumors, and high Ki67 index) [14].