Prognostic Implications of p16 Immunohistochemistry and Its Discordance with Transcriptionally Active HPV in Oropharyngeal Squamous Cell Carcinoma: A Taiwanese Cohort Study.

Background and

Objectives

Oropharyngeal squamous cell carcinoma (OPSCC) is a biologically heterogeneous disease. p16 immunohistochemistry is widely used as a surrogate marker for human papillomavirus (HPV)-associated OPSCC and plays a key role in prognostication and staging. However, p16 overexpression does not invariably reflect transcriptionally active HPV infection, and the clinical significance of p16-HPV discordance remains incompletely defined, particularly in populations with high exposure to traditional carcinogens. Materials and

Methods

We conducted a retrospective cohort study of patients diagnosed with OPSCC between 2016 and 2020 at a tertiary referral center in Taiwan. p16 immunohistochemistry was performed in all cases, and transcriptionally active high-risk HPV was assessed by RNA in situ hybridization in p16-positive tumors. Clinicopathologic characteristics, carcinogen exposure profiles, and survival outcomes, including overall survival (OS) and disease-free survival (DFS), were analyzed according to p16 and HPV status.

Results

Among 140 patients with OPSCC, 49 (35%) were p16-positive, of whom 44 (90%) demonstrated transcriptionally active HPV. Compared with p16-negative tumors, p16-positive OPSCC was significantly associated with lymphoepithelial organ involvement, non-keratinizing morphology, lower clinical stage, and less exposure to alcohol, betel nut, and tobacco. In Kaplan-Meier and univariable analyses, p16 positivity was associated with significantly improved OS and DFS. In contrast, p16-positive/HPV RNA-negative tumors exhibited clinicopathologic features more closely resembling p16-negative OPSCC, including greater keratinization and higher carcinogen exposure.

Conclusions

p16-positive/HPV RNA-negative tumors showed clinicopathologic features suggestive of biological heterogeneity; however, the small number of discordant cases precludes definitive conclusions regarding survival differences. These findings support selective HPV RNA testing in p16-positive OPSCC with atypical clinicopathologic features, particularly in carcinogen-endemic populations.