Incidence of human papillomavirus in oropharyngeal squamous cell carcinomas: now and 50 years ago.

The increasing incidence of oropharyngeal squamous cell carcinomas is believed to be due to the growing proportion of human papillomavirus-positive oropharyngeal squamous cell carcinoma. To examine the time trend in the incidence of human papillomavirus, oropharyngeal squamous cell carcinomas diagnosed from 1956 to 1969 (n = 43) and from 2007 to 2009 (n = 54) were tested by p16 immunohistochemistry and in situ hybridization for human papillomavirus. Morphologically, in these 2 time periods, the predominant type of oropharyngeal squamous cell carcinoma changed from keratinizing to nonkeratinizing, with increase in nonkeratinizing cases from 28% to 67% (P < .001). Also, there was an increase in surgical resections versus biopsies (11% versus 46%; odds ratio, 6.6; P < .001) and base of tongue versus tonsillar location (20% versus 40%; odds ratio, 2.6; P = .04). The proportion of human papillomavirus-positive oropharyngeal squamous cell carcinoma increased from 35% to 72% (odds ratio, 4.9; P < .001). This increase was most apparent in men (odds ratio, 4.2; P < .001). This study provides the earliest historic baseline for human papillomavirus incidence in oropharyngeal squamous cell carcinoma and may serve as a reference point for evaluating the results of human papillomavirus infection preventive measures, such as human papillomavirus vaccination.