A Study of Immunohistochemical Expression of PD-1 and Its Ligand (PDL1) In Head and Neck Squamous Cell Carcinoma

Introduction: Head and neck squamous cell carcinoma (HNSCC) is a common malignancy with high rates of recurrence and poor survival in advanced stages. Immune checkpoint molecules, particularly programmed cell death protein-1 (PD-1) and its ligand PD-L1, have emerged as important therapeutic targets. Their expression in relation to human papillomavirus (HPV)–associated tumors, assessed by p16 immunohistochemistry, remains variable and incompletely understood. Materials and Methods: This observational, cross-sectional analytical study included 30 cases of primary HNSCC. Immunohistochemistry was performed on formalin-fixed paraffin-embedded tissues for PD-1, PD-L1, and p16. PD-L1 expression was assessed in tumor cells based on percentage, intensity, and H-score, while PD-1 expression was evaluated in intratumoral lymphocytes. p16 immunostaining was used as a surrogate marker for HPV infection. Statistical analysis was done to assess concordance between markers. Results: PD-L1 expression was observed in 66.6% of cases, while PD-1 expression in tumor-infiltrating lymphocytes was seen in 76.6% of cases. p16 positivity was noted in 20% of tumors. No statistically significant association was found between PD-L1 and p16 expression (p=0.33), or between PD-1 and p16 expression (p=0.66). Concordance between PD-1 and PD-L1 expression was approximately 70%, which was also not statistically significant (p=0.127). Conclusion: A substantial proportion of HNSCC cases express PD-1 and PD-L1 irrespective of p16 status. These findings suggest that immune checkpoint inhibitor–based immunotherapy may be beneficial in both p16positive and p16-negative advanced or metastatic HNSCC. Larger studies are required to validate these observations and to refine biomarker-based patient selection for immunotherapy.