Immunohistochemical Study of the Tumor Immune Microenvironment in p16-Positive and p16-Negative Oral Squamous Cell Carcinoma and Its Prognostic Implications

Background/Objectives: Oral squamous cell carcinoma (OSCC) is a tumor characterized by heterogeneous clinical behavior and prognosis. The tumor immune microenvironment plays a significant role in tumor progression and patient prognosis. p16 expression has been investigated as a surrogate biomarker in certain subtypes of head and neck squamous cell carcinomas, but its prognostic significance in oral squamous cell carcinoma remains incompletely elucidated. Methods: A retrospective cohort of 59 patients diagnosed with primary oral squamous cell carcinoma was analyzed. Tumor samples were evaluated for p16 expression and immunohistochemical markers associated with immune cell populations. Associations between immune microenvironment features, p16 status, and clinical outcomes such as recurrence and survival rate were analyzed. Results: p16-positive tumors were predominantly associated with immunotype A and exhibited higher densities of CD8+ cytotoxic T lymphocytes and natural killer (NK) cells. In contrast, immunotype B tumors showed similar characteristics regardless of p16 status, with no significant differences between p16-positive and p16-negative cases. Distinct immune profiles were variably associated with clinicopathological features and patient outcomes. Conclusions: These findings suggest that the immunological phenotype of oral squamous cell carcinoma may represent a potential prognostic factor.