The significance of p16 protein expression in oral squamous cell carcinoma.

Introduction: Human papillomavirus (HPV) infection plays an important role in the etiopathogenesis of oropharyngeal squamous cell carcinomas. HPV detection in these tumours is a positive prognostic marker. The p16 protein expression, which is detected immunohistochemically, is an indirect marker of active HPV infection. Unlike in oropharyngeal carcinoma, in oral carcinoma, the prognostic significance of HPV/p16 positivity is unclear. Some studies even show a worse prognosis in patients with HPV/p16 positive oral carcinoma. The aim of our study is to consider the significance of p16 protein expression in relation to clinicopathological parameters and prognosis in patients with oral squamous cell carcinomas.  Methods: One hundred and twenty patients treated surgically for oral carcinoma were enrolled in the study. The most common anatomical sites of oral carcinoma were the tongue body (54; 45% of cases) and floor of mouth (35; 29.2% of cases). All tumours were analysed immunohistochemically for p16 protein expression. The results were correlated with the clinicopathological parameters and analysed statistically.

Results: Ten patients (8.3%) tested positive for p16 expression. In the study cohort, p16 expression was identified as the most significant factor with a negative effect on survival (p=0.019). Based on the Cox proportional hazard model, the p16-positive patients had four times worse survival than the p16-negative ones. Other factors with a statistically significant effect on survival were T status, N status, and recurrence.

Conclusion: The significance of p16 expression differs between oral and oropharyngeal carcinomas. The p16 positivity seems to be a negative prognostic factor in oral carcinomas. Nevertheless, the significance of HPV presence in tumours outside the oropharyngeal area remains unclear.