Simple SummaryThe prevalence of oropharyngeal squamous cell carcinomas (OPSCCs) driven by human papillomavirus (HPV) infection has a wide geographical variability. In addition, several authors have reported steadily increasing prevalence rates over the past two decades. It is important to know the epidemiological landscape of these tumors both to estimate the reliability of diagnostic tests and to guide public health choices aimed at primary prevention. In this retrospective study, we observed a significant increase in the prevalence of HPV-driven OPSCC from 12% during 2000–2006 to 50% during 2019–2022. The use of p16INK4aoverexpression as a surrogate marker of transforming HPV infection should consider the prevalence rates of HPV-driven OPSCC as this significantly impacts on its positive predictive value. Health policies should actively promote vaccination against HPV in both females and males also for the prevention of OPSCC.AbstractBackground: The prevalence and incidence of oropharyngeal squamous cell carcinomas (OPSCCs) driven by human papillomavirus (HPV) infection are increasing worldwide, being higher in high-income countries. However, data from Italy are scanty. p16INK4aoverexpression is the standard in determining HPV-driven carcinogenesis, but disease prevalence impacts on its positive predictive value. Methods: This is a multicenter retrospective study enrolling 390 consecutive patients aged ≥18 years, diagnosed with pathologically confirmed OPSCC in Northeastern Italy between 2000 and 2022. High-risk HPV-DNA and p16INK4astatus were retrieved from medical records or evaluated in formalin-fixed paraffin-embedded specimens. A tumor was defined as HPV-driven when double positive for high-risk HPV-DNA and p16INK4aoverexpression. Results: Overall, 125 cases (32%) were HPV-driven, with a significant upward temporal trend from 12% in 2000–2006 to 50% in 2019–2022. The prevalence of HPV-driven cancer of the tonsil and base of the tongue increased up to 59%, whereas it remained below 10% in other subsites. Consequently, the p16INK4apositive predictive value was 89% for the former and 29% for the latter. Conclusions: The prevalence of HPV-driven OPSCC continued to increase, even in the most recent period. When using p16INK4aoverexpression as a surrogate marker of transforming HPV infection, each institution should consider the subsite-specific prevalence rates of HPV-driven OPSCC as these significantly impact on its positive predictive value.