The Frequency of PD-L1 Marker Expression in ER Positive, PR Positive, HER2 Negative Invasive Breast Carcinomas, and Its Correlation with Clinicopathological Factors Affecting Prognosis.

Background: The aim of this study was to investigate the expression of the PD-L1 marker in ER-positive, PR-positive, and HER2-negative breast carcinoma and examine its correlation with clinicopathological factors that affect prognosis in these patients. Materials and Methods: This cross-sectional descriptive-analytical study was conducted on paraffin-embedded tissue blocks from 50 invasive breast carcinoma patients. PD-L1 immunohistochemical staining was performed, and samples were examined to assess the membranous staining of tumor cells with the PD-L1 marker. ER, PR, and HER2 results were obtained from the pathology reports. The tumor proliferative index was divided into two groups: low proliferative index (<14%) and high proliferative index (= or >14%), based on the percentage of tumor cell nuclei with positive staining. Results: PD-L1 expression was negative in 44 (88%) and positive in 6 samples (12%). There was no significant difference in the mean age, tumor grade, and tumor proliferative index between the two groups ( Conclusion: According to the results of this study, there is no relationship between the PD-L1 expression and well-known clinicopathological prognostic factors in ER-positive, PR-positive, and HER2-negative invasive breast carcinomas.