Immunohistochemical Expression of Programmed Death Ligand 1 (PD-L1) and Its Correlation with Clinicopathological Parameters in Breast Carcinoma

Abstract

Aims: Breast carcinoma (BC) is the leading cause of tumor burden, with an incidence of 11.8%. The programmed cell death protein 1(PD-1)/programmed death ligand 1 (PD-L1) pathway represents an adaptive immune resistance mechanism that tumor cells exert. Recent updates in the treatment modality of breast carcinoma indicate that the use of anti-PD-L1 therapy will help treat advanced breast carcinoma. This study aimed to evaluate the immunohistochemical (IHC) expression of the PD-L1 in breast carcinoma and to analyze the correlation between the PD-L1 and various clinicopathological factors. Study Design:  A hospital-based cross-sectional study. Place and Duration of Study: Department of Pathology, BLDE(DU). Shri B.M. Patil Medical College, Hospital, and Research Center, Vijayapura. Between 1st May 2023 to 31st December 2024.  Methodology: The study was conducted on fifty invasive breast carcinoma cases. Tumor samples were assessed via routine microscopy and graded using the Bloom-Richardson system. IHC was performed for PD-L1 and estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2/neu (HER2/neu) status. PD-L1 scoring was performed using the combined positive score (CPS). PD-L1 expression was then correlated to clinicopathological factors including age, tumor size, histologic type and grade, lymph node status, and pTNM stage. Results: PD-L1 expression was seen in 14 out of 50 cases (28.0%). Expression of PD-L1 showed a statistically significant correlation with HER2/Neu (p = 0.03). The expression of PD-L1 is not statistically significant with other clinicopathological parameters. Hence, PD-L1 may not be a robust prognostic marker based on current evidence. Conclusion: Standardized PD-L1 immunohistochemistry reporting ensures reliable evaluation of breast carcinoma. Consistent and accurate PD-L1 assessment could significantly impact the application of novel targeted immunotherapies in treating breast carcinoma.