Mucosal and skin HPV types in tumour-free tonsils and tonsillar tumours

Human papillomavirus (HPV) infection is associated with tonsillar cancer (TC) whose incidence in humans is increasing. Tonsillar tumours are not ordinarily preceded by clinically apparent precancerous lesions, and no markers of the early stage disease are available. Therefore, we evaluated the presence of an active HPV infection also in tumour-free tonsillar tissue. Formalin-fixed paraffin-embedded (FFPE) tonsillar specimens from 114 patients with TC and 114 age and gender matched controls were screened for the presence of HPV DNA, expression of HR-HPV E6 mRNA, and p16 overexpression. HPV DNA was identified in 3.5% of tumour-free tissues, HR-HPV16 and 58 and LR-HPV111 and 17 were each detected in a single sample. No HR HPV E6 mRNA and p16 overexpression was found. The prevalence of HPV DNA in TC was 69.3%, with HPV16 being the most common (94.9%). Eighty-four percent of HPV16-positive tumours expressed HR HPV E6 mRNA, while no E6 mRNA was present in samples positive for HPV52 and 58. The overexpression of p16 correlated well with HPV DNA in TC, but in tumour-free tonsils no overexpression of p16 was detected.Our data provide further evidence of the etiological role of HPV16 in TC. In tumour-free tissue, the presence of HR-HPVs was rare and silent, as shown by direct and indirect markers.