Cancers coded as tongue not otherwise specified: relevance to surveillance of human papillomavirus-related cancers.

Data from US population-based cancer registries have shown increasing incidence rates for cancer of the base of the tongue, interpreted as related to the epidemic of human papillomavirus (HPV) infection, but rates could be underestimated due to miscoding of some base of tongue cancers to tongue "not otherwise specified" (NOS). Tongue NOS was the most commonly coded subsite among incident (2000-2011) invasive cancers of the oral tongue (tongue excluding base of tongue and lingual tonsil which together comprise the posterior one-third of the tongue) in the 18 Surveillance, Epidemiology and End Results (SEER) Program registries combined and in the Connecticut SEER registry. All 173 cases of tongue NOS cancer in the Connecticut SEER registry diagnosed in selected years were reviewed. Only 5% were recoded to base of tongue, decreasing from over time from 8% to 2%, resulting in minimal impact on the incidence rate for base of tongue cancer in Connecticut. Most (76%) of the 173 tongue NOS cases were recoded to anterior two-thirds of tongue NOS, ruling out base of tongue as the actual site but resulting in underestimation of incidence rates for anterior two-thirds NOS in Connecticut. Similar studies are needed on tongue NOS cancers in other US cancer registries, along with studies on the HPV status of tumors at specific subsites of the oral tongue, to enhance surveillance and interpretation of trends in cancer incidence in relation to the HPV epidemic.