Abstract
Background: Breast cancer is still the most significant cancer-causing mortality among females around the world. Invasive duct carcinoma of no special type is the most prevalent type of breast cancer. So it is essential to search for novel and promising markers detected by immunohistochemistry helping in the prognosis of cancer breast.
Aim of the study: To evaluate programmed death-ligand 1 (PD L1) immunohistochemical expression in invasive ductal carcinoma of the breast of no special type (IDC NST) and to analyze the correlation between PD L1 expression and clinicopathological parameters of cases.
Materials and Methods: A Cross-sectional study was conducted on eighty patients diagnosed with IDC NST enrolled in this study during the period from January 2017 to May 2019 at Zagazig University Hospitals. All lesions were submitted for immunohistochemical analysis using PD-L1 antibody (rabbit monoclonal antibody clone CAL 10), and PD-L1 expression was assessed. Results were correlated with clinicopathological parameters. The resulted data were statistically analyzed.

Results: PD-L 1 expression was detected by immunohistochemistry in 30% (24/80) of breast cancer cases. PD-L1 expression was significantly correlated with well-perceived parameters of poor prognosis, including youthful patient age, high tumor grade, Estrogen and progesterone receptors negative status, necrosis and lymphovascular invasion (p < 0.001, = 0.004,