Squamous cell carcinoma of the oral cavity rarely harbours oncogenic human papillomavirus

Although it is now well established that a significant proportion of oropharyngeal squamous cell carcinomas (SCC) harbour oncogenic human papillomavirus (HPV) sequences, the frequency with which these sequences are detected in oral SCC (excluding oropharyngeal subsites) is highly variable. In an attempt to establish the true prevalence of HPV-16 and HPV-18 subtypes in oral SCC, we screened 142 consecutive cases from a UK cohort using both conventional PCR with consensus primers and type-specific quantitative PCR (Q-PCR), while at the same time employing a rigorous protocol to avoid sample contamination. Q-PCR revealed HPV sequences in five cases; two contained HPV-16 alone, two HPV-18 alone, and one sample carried both genotypes. However, only two of these cases (both HPV-16-positive) had moderate viral loads (51 and 91 viral copies per 100 cells respectively) and were positive for HPV DNA by conventional PCR. Both cases contained HPV DNA in tumour cells as shown by Q-PCR analysis of micro-dissected tissue and by in situ hybridisation. The remaining three cases had only very low viral loads (between 3 and 7 viral copies per 100 cells), were negative by conventional PCR and lacked HPV DNA in tumour cells. Our data provide strong evidence that oncogenic HPV is uncommon in oral SCC and that routine HPV testing of these tumours cannot be advocated.