• crypt epithelium;
  • human papillomavirus;
  • immunostaining;
  • normal tonsil;
  • p16INK4A;
  • polymerase chain reaction;
  • tumour-free tonsil

Klingenberg B, Hafkamp H C, Haesevoets A, Manni J J, Slootweg P J, Weissenborn S J, Klussmann J P & Speel E-J M (2010) Histopathology56, 957–967 p16INK4Aoverexpression is frequently detected in tumour-free tonsil tissue without association with HPV

Aims:  Oncogenic human papillomavirus (HPV) type 16 has been strongly associated with tonsillar squamous cell carcinoma (TSCC) and appears to be of prognostic significance. Because HPV+ TSCC also accumulates p16INK4A, this cyclin-dependent kinase inhibitor has been proposed as a potential biomarker for HPV in clinical diagnosis. The aim of this study was to determine the prevalence of HPV in tumour-free tonsillar tissue and the value of p16INK4A overexpression in predicting its presence.

Methods and results:  p16INK4A overexpression was detected by immunohistochemistry in tissue sections of tumour-free tonsils of 262 patients. They were treated for non-oncological reasons (snoring or chronic/recurrent tonsillitis) consisting of tonsillectomy. Genomic DNA isolated from these tissues was subjected to HPV-specific polymerase chain reaction (PCR) analysis. p16INK4A immunoreactivity was detected in 28% of samples in both crypt epithelium (49/177) and lymphoid germinal centres (52/187), which correlated with each other (P < 0.0001). No reactivity was observed in superficial squamous cell epithelium. HPV16 and 18 were detected by PCR analysis in 2/195 cases (1%), which, however, were negative on fluorescence in situ hybridization analysis and discrepant on p16INK4A immunostaining.

Conclusions:  No proof was found for the presence of HPV in tumour-free tonsil tissue, despite increased p16INK4A expression in a quarter of tonsil cases. Other mechanisms than HPV infection are therefore implicated in p16INK4A up-regulation.