Some evidence links HPV to benign and malignant tumors of the upper respiratory tract. The International Agency for Research on Cancer has found that people with lung cancer were significantly more likely to have several high-risk forms of HPV antibodies compared to those who did not have lung cancer.  Researchers looking for HPV among 1,633 lung cancer patients and 2,729 people without the lung disease found that people with lung cancer had more types of HPV than noncancer patients did, and among lung cancer patients, the chances of having eight types of serious HPV were significantly increased.  In addition, expression of HPV structural proteins by immunohistochemistry and in vitro studies suggest HPV presence in bronchial cancer and its precursor lesions.  Another study detected HPV in the EBC, bronchial brushing and neoplastic lung tissue of cases, and found a presence of an HPV infection in 16. 4% of the subjects affected by nonsmall cell lung cancer, but in none of the controls.  The reported average frequencies of HPV in lung cancers were 17% and 15% in Europe and the Americas, respectively, and the mean number of HPV in Asian lung cancer samples was 35. 7%, with a considerable heterogeneity between certain countries and regions.