["Presence of HPV DNA was analyzed in mouthwash and tonsillar swab samples, if indicative of HPV-positive tonsillar or base of tongue cancer in 76 patients, with suspected head neck cancer, undergoing diagnostic endoscopy at Karolinska University Hospital. The diagnosis and tumor HPV status was later obtained from patients' records. As controls, 37 tumor-free dental visitors were included.", 'Of the 76 patients, 22/29 (76%) and 16/18 (89%) had an HPV-positive tonsillar and base of tongue cancer respectively, with 18/22 (82%) and 8/16 (50%) respectively having tumor concordant HPV-type positive oral samples. Two other HPV-positive oral samples in the base of tongue cancer group did not correlate to the tumor HPV status. Among the remaining patients, 19 with other head neck cancer and 10 with benign conditions, 4/29 (14%) had HPV-positive oral samples. Consequently, of the HPV-positive oral samples, dominated by HPV16 and high signals, 27/32 (84%) were derived from 26 patients with concordant HPV-type positive tonsillar or base of tongue cancer and one patient with an unknown primary head and neck cancer. The other five HPV-positive oral samples, with mainly low signals were derived from two patients with non-concordant HPV-type positive tumor biopsies, two patients with HPV-negative tumor biopsies and a patient with a benign condition. Of the dental patients, 3/37 (8%) had HPV-positive tonsillar swabs with weak signals.'] Is human papillomavirus prevalence high in oral samples of patients with tonsillar and base of tongue cancer?