Expression of PD-L1 in invasive ductal carcinoma of the breast and its correlation with HER2/neu and Ki-67: a study from a tertiary care center

Abstract

Background. Programmed death-ligand 1 (PD-L1) expression in breast carcinoma has gained increasing attention as a potential prognostic and predictive biomarker and as a marker relevant to immunotherapy. Aim. To evaluate PD-L1 expression in invasive ductal carcinoma (IDC) of the breast and its correlation with HER2/neu and Ki-67 expression. Methods. This prospective, cross-sectional study included 36 mastectomy, lumpectomy, and tru-cut biopsy specimens of IDC analyzed between March 2021 and October 2022 at the Department of Pathology, Sree Balaji Medical College, Chennai. Immunohistochemistry was performed using antibodies against PD-L1, HER2/neu, and Ki-67. Statistical analyses were conducted using SPSS version 16. Categorical data were compared using the chi-square test or Fisher’s exact test, as appropriate, and p-values <0.05 were considered statistically significant. Results. The mean age of the patients was 53.8 years. Most tumors were histological grade 2 (55.6%). PD-L1 positivity (IHS ≥3) was observed in 44.4% of cases and was significantly associated with HER2/neu overexpression (p = 0.024). A positive association with a high Ki-67 index was observed but was not statistically significant (p = 0.077). Conclusion. PD-L1 expression showed a significant association with HER2/neu positivity and a non-significant association with a high Ki-67 proliferation index. These findings suggest a relationship between PD-L1 expression and other biomarkers of breast cancer biology; however, larger studies with patient outcome data are required to assess its prognostic value and therapeutic implications.