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Background Lower prevalence HPV infection has been previously reported in Thai population when compared with Western countries. p16 expression indicates HPV-associated oropharyngeal squamous cell carcinoma (OPSCC), but not non-OPSCC. We therefore evaluated the characteristic and association of p16 and HPV in Thai patients with HNSCC. Methods We used immunohistochemistry and qPCR, respectively, to detect p16 and HPV DNA in archrival formalin-fixed paraffin-embedded HNSCC tissues. Patient characteristics and survival were analyzed. Results p16 expression was detected in tumors of 72 of 662 (10.9%) patients with HNSCC and was significantly associated with higher-grade histology, advanced nodal stage, and oropharynx. p16 was expressed in 28 and 6.5% of patients with OPSCC or non-OPSCC, respectively, and HPV DNA was detected in 15.6 and 1% of patients, respectively. Using p16 as a surrogate for HPV status, sensitivities were 80 and 25% in OPSCC and non-OPSCC, respectively. Positive and negative predictive rates of OPSCC were 38 and 95%. Discordance rates between HPV and p16 were 23 and 7% in OPSCC and non-OPSCC, respectively. Overall survival (OS) were significantly longer in both p16-positive OPSCC (p = 0.049), and non-OPSCC (p = 0.003). Conclusions Low prevalence of p16 and HPV associated OPSCC and non-OPSCC were confirmed in Thai patients. High discordance and low positive predictive rates of p16 were observed in HPV-associated OPSCC. p16 was a significant prognostic factor for OS for patients with OPSCC or non-OPSCC. Therefore, HPV testing should be performed to assess the association of HPV with HNSCC regardless of p16 expression.

Additional file 1: Supplement 1. Real-time PCR typing of HPV with AmoyDx High-risk Human Papillomavirus (HPV) Detection Kit. One reaction with three fluorescents (A:FAM-other 17 HPVs high risk, B: Cy5-HPV 16/18 and C: HEX-Internal control) were mixed in each reaction tube for identification of the 19 possible HPV high risk types in a real-time PCR setting, as described in the Material and Methods section (1: positive control, 2: no template control, 3: positive other 17 HPVs high risk sample, 4: positive HPV type 16 or 18 sample and 5: internal control of sample). Supplement 2. Baseline characteristics of non-oropharyngeal HNSCC and p16 status.