Immunohistochemical expression of programmed death ligand 1 in squamous cell carcinoma of head and neck

Objective: To assess the immunohistochemical expression and clinicopathological features of Programmed Death Ligand 1 in the head and neck squamous cell carcinoma (HNSCC). Material and Methods: This Cross-sectional study was conducted at the Histopathology department, Rehman Medical Institute, Peshawar, Sep 2023 to Dec 2024. Patients with histologically confirmed head and neck squamous cell carcinoma were included in the study. Sections from Formalin fixed tissue blocks underwent immunohistochemical staining by PD-L1 antibody followed by analysis. Demographic characteristics and histopathological parameters were recorded. Results: Among 92 participants we observed a male predominance with male to female ratio of 3.8:1 with a median (IQR) age of 59.62 (56.85-62) years. The frequency of PD-L1 positivity was observed in 84 (91.3%) patients. The most common site of the tumor was the oral cavity in 56 (60.9%). We observed that lymphovascular and perineural invasion was not significantly associated with PD-L1 positivity. T-stage of the tumors revealed that most tumors had T1 followed by T2 stage, while N-staging revealed most specimens 39 (46.4%) had N1 stage, followed by N0, N3, and N2 stage with a significant correlation to PD-L1 positivity. Tumors with extranodal extension and moderate tumor-infiltrating lymphocytes histologically revealed PD-L1 expression in 30 (35.7%) and 59 (70.2%) with p-0.920 and p-0.239 respectively. Conclusion: We conclude that there is a predominance of PD-L1 positivity in HNSCC with a significant correlation between PD-L1 positivity and nodal metastasis. These findings may lead to the development of immunotherapeutic strategies and identification of patients who may benefit from PD-L1 targeted therapies. Keywords: Immunohistochemistry, PD-L1, Squamous cell carcinoma of head and neck, Immunotherapy