p16 Immunoexpression in sinonasal and nasopharyngeal adenoid cystic carcinomas: a potential pitfall in ruling out HPV-related multiphenotypic sinonasal carcinoma.

p16 staining alone, even when diffuse and strong, cannot be used as a surrogate for HPV testing to distinguish sinonasal AdCC from HMSC. p16 IHC should be accompanied by more specific methods, such as mRNA ISH, so as not to erroneously diagnose HMSC over sinonasal AdCC, bearing in mind the highly aggressive nature of the latter.