The College of American Pathologists has released updated, evidence-based guidelines for human papillomavirus testing in head and neck carcinomas, expanding upon its 2018 recommendations with seven strong recommendations, four conditional recommendations, and five good practice statements.

In the updated guidelines, published in the Archives of Pathology & Laboratory Medicine, investigators, led by James S. Lewis Jr, MD, provided refined testing strategies for various anatomic sites and addressed key areas such as human papillomavirus (HPV) testing in sinonasal squamous cell carcinoma (SNSCC), specific interpretation criteria for p16 immunohistochemistry (IHC), and testing recommendations for fine-needle aspiration (FNA) specimens.

"Substantial new evidence has prompted a review, including data on [HPV] in nonoropharyngeal anatomic sites, HPV global rates, p16 [IHC], and HPV testing performance in cytology specimens, and performance of p16 immunohistochemistry as a surrogate marker," the guideline authors wrote.

A significant addition to the guidelines is the recommendation for routine HPV testing in SNSCC. Evidence from multiple studies demonstrated that HPV-associated SNSCC has a more favorable prognosis compared with HPV-independent SNSCC. For sinonasal specimens, the investigators specifically recommend directly testing for transcriptionally active HR-HPV using RNA in situ hybridization (RNA-ISH), with p16 IHC potentially used as a screening tool for confirmatory HPV-specific testing.

For oropharyngeal tissue specimens, the invvestigators maintain that p16 IHC is an appropriate surrogate marker in most cases, but specify that HPV-specific testing should be performed in certain scenarios, including:

• Geographic regions with low prevalence of HR-HPV-associated OPSCC
• When p16 immunostaining is equivocal (50% to 70% staining or when staining is extensive but weak)
• When discrepancy exists between p16 staining and morphology
• For large, multisite tumors overlapping the oropharynx
• When specimens are from a nontonsillar, non–base of tongue oropharyngeal site
• When required by clinical trials.

The investigators established definitive criteria for p16 IHC interpretation, stating: "For tissue specimens, when p16 IHC is indicated, pathologists should report it as positive (and as a surrogate for HR-HPV) when there is at least 70% nuclear and cytoplasmic expression with at least moderate to strong intensity."

For FNA specimens, the recommendations emphasize HPV-specific testing rather than p16 IHC. "For FNA specimens, pathologists should perform HPV-specific testing," the guideline authors stated, noting: "In selected circumstances, p16 IHC can be performed instead of HPV-specific testing. If the result of HR-HPV testing on the FNA sample is negative, testing should be performed on tissue if it becomes available." Notably, the investigators underscored that p16 IHC alone is less reliable in FNA specimens as a result of variability in performance and its significantly lower accuracy compared with RNA-ISH.

The expert panel recommends using HPV-specific tests that exhibit optimal performance characteristics, specifically stating: "Pathologists should use tests that exhibit optimal performance characteristics—such as RNA-ISH or DNA PCR—and have adequate coverage of non-HPV 16 high-risk types." The guidelines specifically don't recommend DNA-ISH because of its lower sensitivity, particularly at low viral loads.

For recurrent or metastatic disease, the investigators recommend against routine repeat HPV testing if primary tumor HR-HPV status has already been established, though testing may be performed on a case-by-case basis for diagnostic purposes if there is uncertainty regarding whether a tumor is a recurrence or a new primary malignancy.

The investigators also included a strong recommendation against providing tumor grade or differentiation status for HPV-associated OPSCCs, since traditional grading has limited clinical utility and can paradoxically lead to "poorly differentiated" tumors having the best prognosis because of their association with HR-HPV.

The multidisciplinary panel used the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach to evaluate the strength of evidence, with strong recommendations indicating a high level of evidence and consensus that benefits clearly outweigh harms.

The investigators noted some limitations, particularly regarding rare HPV-associated nonsquamous cancers and the limited data available on sinonasal squamous cell carcinoma. Further research is needed to address these gaps.

Complete disclosures of the expert panel members are available in the guidelines.