CDKN2A and oropharynx cancer: Differences in methods of HPV-testing usually hamper precise comparisons of HPV-prevalence over time and study population – an important advantage of the highly standardized study protocol and the single-centre HPV-DNA detection and genotyping in the study by Castellsagué et al. The authors further describe an increasing proportion of HPV-positive oropharyngeal cancer cases over time (worldwide): only about 10% of oropharyngeal cancer cases diagnosed in the 1990s were HPV-DNA-positive and mRNA-positive/p16-positive.