Utility of Programmed Cell Death Ligand One (PDL1) Expression for Assessing Tumour Behaviour in Comparison to Histopathological Grading and TNM Staging in Oral Squamous Cell Carcinoma Patients: A Research Protocol for a Cross-sectional Study

Introduction: Conventional prognostic indicators such as histopathological grade and TNM staging often fail to fully capture the heterogeneity in tumour behaviour. Recent advances in molecular pathology have highlighted the role of immune checkpoint markers, particularly Programmed Cell Death Protein 1 (PD-1)/Programmed Cell Death Ligand-1 (PDL1), in tumour progression and immune evasion. Evaluating PD-L1 expression in Oral Squamous Cell Carcinoma (OSCC) may therefore provide important insights into prognosis and therapeutic strategies. Need of the study: Although PD-L1 has been recognised as a predictive biomarker in several malignancies, its diagnostic and prognostic utility in OSCC, especially within the Indian population, is inadequately studied. Given the high incidence of OSCC in India and the limited effectiveness of conventional prognostic tools, assessing PD-L1 expression in relation to histological grading and TNM staging is essential. Such findings may refine risk stratification, improve patient outcomes, and aid in integrating immunotherapy into treatment protocols. Aim: To evaluate the role of PD-L1 expression as an immunohistochemical marker in assessing tumour behaviour in OSCC and compare its utility with histopathological grading and TNM staging. Materials and Methods: The present two-year observational cross-sectional study will be conducted from April 2024 to April 2026 in the Department of Pathology, Jawaharlal Nehru Medical College, Sawangi (Meghe), in collaboration with Oral Surgery, Sharad Pawar Dental College and Hospital, Sawangi, Wardha, Maharashtra. Ninety-five histopathologically confirmed OSCC cases will be included. Formalin-fixed paraffin-embedded sections will undergo Haematoxylin and Eosin (H&E) staining for histological grading (CAP guidelines) and staging (AJCC 8th edition). PD-L1 immunohistochemistry will be performed using clone 22C3 (Dako), and expression scored by Combined Positive Score (CPS), with CPS <1 negative and CPS ≥1 positive. Tonsillar carcinoma will serve as the positive control and omission of secondary antibody as the negative control. Associations between PD-L1 expression, grade, and TNM stage will be tested by Chi-square, with p<0.05 considered significant.