Expression of immune checkpoint protein in oral squamous cell carcinoma and its clinicopathological correlation: A tertiary care center cross-sectional study.

Background: Recent evidence suggests that oral squamous cell carcinoma (OSCC) patients who exhibit the immunohistochemical expression of immune checkpoint protein programmed cell death ligand 1 (PD-L1) are more likely to have a poor clinical outcome and may serve as an independent prognostic marker. Aims and Objectives: This study aimed to assess the immunohistochemical expression of immune checkpoint protein PD-L1 in OSCC and its clinicopathological correlation. Materials and Methods: OSCC cases were included in the study. This was a tertiary care center cross-sectional one-year duration study. Histomorphological diagnosis and immunohistochemical expression of PD-L1 were performed after taking ethical clearance. The statistical analysis was performed using Statistical Package for Social Sciences (SPSS) version 21.0 statistical analysis software. Results: A total of 106 cases of OSCC were included in the study. Histologically, the majority of cases (58.5%) were graded as well differentiated, followed by moderately differentiated (58.5%) and poorly differentiated (4.7%), respectively. In PD-L1 immunohistochemical expression, score 1+ was accorded to 37 (34.9%), 2+ was accorded to 31 (29.2%), and score 3+ was accorded to 33 (31.1%) cases. Tumor size, pattern, depth of invasion lymphovascular invasion (LVI), and perineural invasion (PNI) were found to be significantly associated with PD-L1 immunohistochemical scores. Conclusions: We concluded that the immunohistochemical expression of immune checkpoint protein PD-L1 positivity in tumor cells was seen in the majority of the cases (60.37%) in our patient. This suggests that the PD-1 or PD-L1 pathway plays a significant role in tumor immune evasion in OSCC.