A non-oropharyngeal squamous cell carcinoma and the pitfalls of HPV testing: A case report

Background: High-risk human papilloma virus (HPV) is a driver of the development of oropharyngeal squamous cell carcinomas (SCC), while its role in other head and neck subsites, including the oral cavity, is debated. HPV detection in tissue is assayed directly and indirectly using various methods, including p16 surrogate immunohistochemistry (IHC), polymerase chain reaction (PCR), and in-situ hybridization (ISH). Methods: Case of a 76-year-old man presenting with a right retromolar trigone well-differentiated keratinizing SCC, which was resected with a free flap reconstruction and HPV/p16 testing. Results: Synchronous p16 IHC and HPV PCR testing of the primary tumor were negative and positive, respectively, whereas testing of a lymph node metastasis by both assays was negative. RNA ISH was negative in the primary tumor and in the lymph node metastasis. Conclusions: HPV assessment of oropharyngeal SCCs, but not those of other subsites, should be performed by surrogate p16 IHC, with any additional HPV confirmational testing done at institutional discretion. Detection of transcriptionally active HPV E6/E7 RNA by ISH may represent a new gold standard.