Immunohistochemical Expression of Programmed Death-Ligand 1 (PD-L1) in Breast Carcinoma and Its Correlation With...

Programmed death-ligand 1 (PD-L1) has become both a therapeutic target and a predictive biomarker in breast cancer, yet reported expression rates vary widely and data from Indian populations remain limited. The primary aim of this study was to examine PD-L1 expression by immunohistochemistry in invasive breast carcinoma and to assess its relationship with histological grade and other clinicopathological variables. As a secondary aim, we evaluated the correlation of PD-L1 expression with estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2/neu) status.

This single-centre observational study analysed 61 histologically confirmed cases of invasive breast carcinoma of no special type at L.N. Medical College and J.K. Hospital, a tertiary care teaching hospital in Bhopal, central India. PD-L1 was scored using an immunohistochemical score (IHS) derived from staining intensity multiplied by the proportion of positive tumour cells, with an IHS of 3 or more taken as positive. ER and PR were regarded as positive at 1% or more nuclear staining, and HER2/neu was scored using American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) criteria; receptor status was assessable in 20 cases. Associations were tested using the chi-square and Fisher's exact tests, with a p-value below 0.05 considered significant.

PD-L1 positivity was present in 14 of 61 tumours (23.0%). Expression rose steadily with histological grade, from 0% in grade I to 16.7% in grade II and 42.1% in grade III, and this association was statistically significant (χ² = 6.533, p = 0.038). PD-L1 positivity was numerically higher in ER-positive than in ER-negative tumours (44.4% vs. 9.1%), in PR-positive than in PR-negative tumours (44.4% vs. 9.1%) and in HER2/neu-positive than in HER2/neu-negative tumours (37.5% vs. 16.7%), but none of these differences reached significance (p = 0.127, 0.127 and 0.347, respectively). No significant association was found with age, tumour size, lymphovascular invasion, an in situ component, or pathological tumour (T) and node (N) stage.

PD-L1 was expressed in roughly one in four invasive breast carcinomas and was significantly associated with higher histological grade, supporting its link with poorly differentiated, biologically aggressive tumours. The trends observed with hormone receptor and HER2/neu status did not reach statistical significance and were limited by the small receptor-tested subset (n = 20), and these findings should therefore be regarded as hypothesis-generating. Larger, multicentre studies with complete molecular subtyping, standardised companion-diagnostic assays, and survival data are needed to confirm these relationships and to define the role of PD-L1 testing in selecting patients for immune checkpoint therapy.