Epidemiology of cancer from the oral cavity and oropharynx.

The classification of sites in tumors of the oral cavity, oropharynx, pharynx, and hypopharynx varies in the literature. More than 90% of these tumors of the mucosal lining are classified as squamous cell carcinoma developed from premalignant lesions such as leukoplakia and erythroleukoplakia. These carcinomas are associated to environmental and lifestyle risk factors, among which tobacco and alcohol play a major role. In addition to tobacco smoking, tobacco chewing is another risk factor as well as chewing betel quid and areca nut in Asia. Certain strains of virus, such as the sexually transmitted human papilloma virus, also play a carcinogenetic role. The temporal trends in incidence of these tumors relate to environmental factors; there is an increase in tendency in countries without prevention and a decrease in countries having an active policy of prevention of alcohol and tobacco consumption. In contrast, an increased incidence occurs in the world at tumor sites related to human papilloma virus infection in relation to changes in sexual habits.