High-risk HPV-related squamous cell carcinoma in the temporal bone: a rare but noteworthy subtype.

High-risk human papillomavirus (HPV) is a risk factor for the development of several head and neck squamous cell carcinomas (SCCs). However, there have been few reports of high-risk HPV infection in temporal bone squamous cell carcinomas (TBSCCs), and thus the prevalence and clinicopathologic significance of high-risk HPV in TBSCCs are still unclear. We retrospectively collected 131 TBSCCs and analyzed them for transcriptionally active high-risk HPV infection using messenger RNA in situ hybridization; we also assessed the utility of p16-immunohistochemistry (IHC) and Rb-IHC to predict HPV infection. Eighteen (13.7%) of the 131 TBSCCs were positive for p16-IHC, and five of them were positive for high-risk HPV infection (the estimated high-risk HPV positivity rate was 3.8% [5/131]). Interestingly, all five HPV-positive patients were male and had TBSCC on the right side. In the p16-IHC+/HPV+ cases (n = 5), the Rb-IHC showed a partial loss pattern (n = 4) or complete loss pattern (n = 1). In contrast, all p16-IHC-negative cases (n = 113) showed an Rb-IHC preserved pattern. The positive predictive value (PPV) of p16-IHC positivity for high-risk HPV infection was low at 27.8%, while the combination of p16-IHC+/Rb-IHC partial loss pattern showed excellent reliability with a PPV of 100%. The prognostic significance of high-risk HPV infection remained unclear. High-risk HPV-related TBSCC is an extremely rare but noteworthy subtype.