Clinicopathological Significance of Immunohistochemical PD-L1 and Androgen Receptor Expressions in Triple Negative Breast Cancers

Objective: Triple negative breast cancers(TNBC), a subset of breast cancers, despite the wide range of morphologies, are high-grade, and related to younger age, higher incidence of metastases, higher risk of recurrence and poorer prognosis. Currently, there is increasing evidence of a dynamic interaction between the immune system and breast cancer. Additionally, the Luminal Androgen Receptor(LAR) subtype, one of the four subtypes of TNBC, is dependent on Androgen Receptor(AR) signaling, and represents a novel subtype of TNBC with a distinct prognosis that offers an opportunity for the development of targeted therapeutics. In this study, we aimed to investigate the immunohistochemical expression of Programmed death ligand 1(PD-L1) and AR and their correlations with clinical parameters in TNBC and to determine the groups suitable for targeted therapy. Materials and Methods: Sixtyfour patients who received a primary diagnosis of TNBC from surgical material at Aydın Adnan Menderes University between 2013-2019 were available for this study. Demographic and histopathological characteristics were obtained from archival reports. PD-L1 and AR immunohistochemical stains were applied to sections prepared from the blocks. Results: The mean age was 53,47±15,044(range 28-84 years). The percentage of PD-L1 positivity was %57,8 and AR positivity was %26,6. There was a significant correlation PD-L1 positivity with Ki67 proliferation index(p=0.009), and lymphovascular invasion(p=0.009) and no correlation between PD-L1 and other parameters. Conclusion: PD-L1 and AR are important prognostic markers for TNBC and identify important groups for targeted therapies. PD-L1 positive cases are associated with poor prognostic markers and further studies in larger groups are needed for both markers.