Expression of Programmed Death Ligand-1 in Head and Neck Squamous Cell Carcinoma: A Cross-sectional Study

Introduction: Head and Neck Squamous Cell Carcinoma (HNSCC) is among the most prevalent malignancies worldwide, with poor survival outcomes despite advances in multimodal therapy. Tumour immune evasion through the Programmed Death-1/Programmed Death Ligand-1 (PD-L1) PDL-1/PD-L1 immune checkpoint pathway has emerged as a crucial mechanism in HNSCC progression. PD-L1 expression, detectable by Immunohistochemistry (IHC), is a promising predictive and prognostic biomarker, especially when evaluated alongside histological grading systems such as Anneroth’s multifactorial grading. Aim: To evaluate PD-L1 expression in HNSCC using IHC and associate it with Anneroth’s histological grading. Materials and Methods: This cross-sectional study conducted at Pt. B.D. Sharma Postgraduate Institute of Medical Sciences, Rohtak over a one-year period from 1st December 2023 to 31st December 2024 included 60 histologically confirmed cases of HNSCC. Histopathological diagnosis was established on routine Haematoxylin and Eosin (H&E) stain. Tumours were classified and graded according to WHO criteria and Anneroth’s multifactorial grading system. PD-L1 expression was assessed using IHC and quantified by the Combined Positive Score (CPS). The status of PDL-1 was assessed and association with various clinicopathological prognostic parameters including age, gender, histologic type, histologic grade, Anneroth`s grading parameters and CPS score. The collected data were analysed with the help of Statistical Package for Social Sciences (SPSS) version 24.0. All the data enlisted in the investigation proforma (name, age, gender, clinical diagnosis and history) were collected. Cases were compared to controls. Association was evaluated using Chi-square test. The p-value less than 0.05 were accepted as statistically significant. Results: Age of the patients ranged from 31-90 years with a median age of 58.0 years. The majority of cases, 21 (35.0%) were in the age group of 51-60 years. 47 (78.3%) cases were male and 13 (21.7%) cases were female. A 13 (21.7%) cases were well-differentiated, 37 (61.7%) cases were moderately differentiated and 10 (16.7%) cases were poorly differentiated SCC. In Anneroth’s multifactorial grading system, majority of cases i.e., 37 (61.7%) assigned grade 2, 12 (20.0%) cases were assigned grade 1, 10 (16.7%) cases assigned grade 3 and one (1.7%) cases assigned grade 4. PD-L1 positivity was observed in 45 (75%) cases, with 26 (43.3%) cases showing low expression (CPS 1-20) and 19 (31.7%) cases showing high expression (CPS ≥20). PD-L1 expression was significantly associated with World Health Organisation (WHO) histological grading, with the highest prevalence among moderately differentiated tumours (p-value=0.037). Similarly, PD-L1 expression positively correlated with higher Anneroth's grades (p-value=0.020). No significant association was found between PD-L1 expression and age (p-value=0.079) or presenting complaints (p-value=0.764). Conclusion: PD-L1 expression in HNSCC is significantly associated with both WHO and Anneroth’s histological grades, highlighting its role in tumour aggressiveness and immune evasion. Incorporating PD-L1 profiling alongside detailed histopathological grading provides valuable prognostic information and may guide patient selection for immune checkpoint inhibitor therapy.