Utility of p16 andHPVtesting in oropharyngeal squamous cell carcinoma: An institutional review

Background In the US, 60% to 80% of oropharyngeal squamous cell carcinomas (OPSCCs) are associated with human papillomavirus (HPV). However, until recently, no consensus existed about when and how to test for HPV in patients with head and neck cancers. We aimed to evaluate the use of p16 and HPV testing at our institution because p16 immunohistochemistry is reportedly a reliable surrogate marker for HPV detection in OPSCCs. Methods We identified all cases at our institution of primary or metastatic squamous cell carcinoma (SCC) of the head and neck with a concurrent p16 immunostain analysis from January 1, 2013, through August 31, 2018. Patient demographic data, tumor characteristics, p16 result, and any HPV result (in situ hybridization and E6 and E7 RNA test) were captured. Results We identified 104 patients. Most primary tumors (53/57 [93.0%]) and metastases (40/47 [85.1%]) were positive for p16. Thirty-seven cases (35.6%) had reflex high-risk HPV (HR HPV) testing performed. Of the 35 p16-positive cases, 6 had discrepant HR HPV results (p16(+)/HPV-). We identified 47 p16 immunostains that were performed on lymph nodes with primary tumors of unknown origin. Most were cytology cases (34/47 [72.3%]), and most were p16 positive (40/47 [85.1%]). Neither tumor differentiation nor tumor keratinization was predictive of p16 positivity. Tumors with basaloid differentiation were universally p16 positive. Conclusion p16 immunohistochemistry accurately identifies HPV-positive OPSCC. Cytology specimens have an important role in characterizing SCC of unknown origin. HR HPV testing is not routinely required, and results may be discrepant with p16 findings.