In which type of cancer is p16 testing not mandatory?

p16 is a tumor suppressor protein that is commonly used as a biomarker to determine the role of human papillomavirus (HPV) in oropharyngeal squamous cell carcinoma (OSCC). In head and neck cancers, particularly oropharyngeal cancers and throat cancers, p16 testing has become crucial because it helps to identify HPV-related malignancies, which can differ in treatment response and prognosis compared to non-HPV related cancers.

Hypopharyngeal cancers, however, generally do not have a significant association with HPV, and hence, p16 testing is not deemed mandatory in their diagnosis and management. These cancers primarily arise in a region of the throat that includes the area just below the oropharynx. Up until this point, the relevance of HPV and the role of p16 in hypopharyngeal cancers have not been established in the same way they have for oropharyngeal and other upper throat cancers. Therefore, while p16 may be useful in some contexts, it is not considered essential for hypopharyngeal cancers.

In the context of the other cancer types listed, oropharyngeal and throat cancers have recognized guidelines that often require p16 testing to inform treatment