Virus-associated carcinomas of the head & neck: Update from the 2017 WHO classification.

Virus-associated carcinomas of the head and neck represent an unusual confluence of infections spread by viral transmission and cellular dysregulation resulting in carcinogenesis. While much remains to be elucidated about the exact progression from infection to cancer, a basic framework of viral biology can complement the pathologist's understanding of morphology. This context informs the pathologist's everyday practice, including selecting ancillary studies, communicating prognostically relevant findings, and participating in treatment planning. By comparing and contrasting the salient features of human papillomavirus-associated oropharyngeal carcinoma and Epstein-Barr virus-associated nasopharyngeal carcinoma, this review summarizes recent evidence to guide current practice.