Background: Triple-negative breast carcinoma has an aggressive nature, poor prognosis, with high recurrence rates and metastasis. It has a poor response to targeted therapies, leaving a restricted number of efficient treatments, including chemotherapy and radiotherapy. Some types of triple-negative breast carcinoma are considered immunogenic types, which mean that these tumors may be susceptible targets to a new line of treatment known as immunotherapy. Several biomarkers have been discovered to determine patients who could be eligible candidates to receive immunotherapies. One of these biomarkers is the programmed death receptor 1 (PD1)/ programmed death ligand 1 (PD-L1) overexpression.

Objectives: To assess the expression status of the PD-L1 protein in a group of triple-negative breast carcinoma patients, and its correlation with the clinicopathological parameters.

Methods: The study was conducted from October 2024 to April 2025. A cross-sectional study involved 53 patients, who were diagnosed as triple-negative invasive ductal breast carcinoma. The formalin-fixed paraffin-embedded blocks were retrieved from the archives department of the histopathological laboratories in the Medical City Complex hospitals, Baghdad, Iraq. The clinical data of these patients were reviewed, and the blocks were sectioned, prepared, and stained with monoclonal anti-PD-L1 antibody.

Results: The majority of the cases (45 patients, 84.9%) had negative expression of PD-L1 protein, while eight patients (15.1%) had positive expression of PD-L1 protein. A non-significant correlation was found between the PD-L1 protein expression and the clinicopathological parameters.

Conclusion: The vast majority of the studied cases had a negative expression of PD-L1 protein. It seemed that the correlation between PD-L1 expression status and the studied clinicopathological parameters was not significant.