Oropharyngeal cancers: significance of HPV16 detection in neck lymph nodes

An increasing proportion of oropharyngeal squamous cell carcinomas (OPSCCs) is associated with human papillomavirus (HPV) type 16 infection. Several authors have suggested that HR-HPV DNA could be used as a marker of metastases in cervical cancers. Although HPV16 DNA has been detected in neck lymph node (LN) metastases of HPV16-positive OPSCC, its significance remains controversial. Does this presence correlate to metastatic involvement or is it just the consequence of LN filter function?

This study aims to analyse the relationship between HPV16 detection in neck LNs of HPV16-positive OPSCC and their pathological status.

HP16-viral load (VL) was quantified by real-time-polymerase-chain reaction in primary tumours and neck LNs, in 11 patients with HPV16-positive OPSCC and in three patients with HPV16-negative OPSCC. HPV16 in situ hybridisation and p16 immunohistochemistry were performed in all LNs.

A total of 45 LN levels were assessed. HPV16 DNA was not identified in HPV16-negative OPSCC LNs. All metastatic LNs from HPV16-positive OPSCC had a high VL and the viral DNA was located within tumoural cells. Among 27 pathologically tumour-free LN (PTFLN) levels 16/27 had no detectable VL, whereas the VL was low or medium (<10(5)copies/million cells) in 8/27 and high (>10(5)copies/million cells) in 3/27 PTFLN. In the latter group, no metastatic cell was identified and the viral DNA was located in immune cells.

HPV16 detection in LN is explained by its presence within either metastatic cells or immune cells. HPV16 detection in PTFLN is not necessarily correlated to occult LN metastases.