Age-adjusted incidence trends by calendar year of diagnosis for head and neck squamous cell carcinoma (HNSCC) by sites and gender.

<p><i>Panel a</i> and <i>b</i> show a significant decrease in the incidence of HNSCC from human papillomavirus (HPV)-unrelated sites (the oral cavity and the larynx/hypopharynx) in males; for females a significant increase was observed for oral cavity HNSCC and a stable trend for larynx/hypopharynx HNSCC. The incidence of HNSCC from HPV-related sites has been significantly increasing in females, but it is stable in males; bars indicate the 95% confidence interval.