Human papillomavirus in metastatic squamous carcinoma from unknown primaries in the head and neck: a retrospective 7 year study.

Goal: Human Papillomavirus (HPV) is found to be increasingly implicated in head and neck cancers. The objective of this study was to determine the primary site of origin of HPV positive squamous carcinomas metastatic to lymph nodes of the neck.
Methods: Surgical pathology records from January 1, 2000 to July 31, 2007 were used to identify surgically removed neck lymph nodes with the diagnosis of metastatic squamous carcinoma. Specimens in formalin-fixed, paraffin-embedded blocks were examined for HPV (+) by analyzing sequencing data generated by PCR and immunostaining for the expression of the p16INK biomarker, which is overexpressed if Rb is not present. H & E stained slides were also reviewed for histological classification. The available retrospective demographics were extracted from the charts to determine trends of confounding factors.
Results: Of the 43 patient samples, 41 contained adequate DNA to test for HPV. The mean age of the 41 patients was 62 years. All of the patients smoked and 39/41 patients consumed alcohol. The overall HPV (+) incident rate was 27% (11/41) by PCR with strongly diffuse or strong focal p16 staining. 9 of the 34 males and 2 of the 7 females had HPV (+) carcinomas. The average age of the 2 HPV (+) females was 44, compared to the HPV (-) females who averaged 70. The average age of the HPV (+) males was 56 compared with the average age 55 of the HPV (-) males. HPV (+) carcinomas appeared to arise from multiple sites in the oropharynx, particularly the tonsils and tongues, including unknown primaries. By histological exam, most metastatic HPV(+) squamous carcinomas were poorly differentiated (basaloid) microscopically and grossly cystic.
Conclusion: The 27% HPV (+) squamous cancers metastatic to neck lymph node originated from multiple sites in the oropharynx. The HPV (+) female population, although a total of only 2, tended to be much younger than the HPV (-) ones, whereas the HPV (+) male population was similar in age to the HPV (-) male population.