The term ‘oral cancer’ encompasses all malignant neoplasms affecting the oral cavity. The majority, greater than 90%, are squamous cell car¬cinomas. The remainder are uncommon and comprise minor salivary gland adenocarcinomas, malignant melanoma, sarcomas, haemato-logical malignancies, and metastases to the oral cavity from cancers at other sites. Oral squamous cell carcinoma is a malignant epithelial neoplasm that arises from the lining mucosa of the oral cavity. The tumour shows vary¬ing degrees of squamous differentiation and is characterized by invasion of local structures and metastasis to regional lymph nodes, followed by metastasis to other organ systems (e.g. lungs and bones) later in the course of the disease. Epidemiological data pertaining to oral cancer can be difficult to evalu¬ate because of variations in the methods of data collection (Box 3.1). Notwithstanding these confounding variables, a database produced by the International Agency for Research on Cancer (GLOBOCAN), esti-mated there were over 400,000 new cases of lip, oral, and pharyngeal cancer worldwide in 2012, placing the disease in ninth position with breast, prostate, lung, colorectal, cervical, stomach, liver, and uterine cancer being more common. These data suggest that oral cancer is uncommon, but there are enormous variations worldwide. Whereas oral cancer is relatively uncommon in the UK, accounting for 2% of all cancers, in India and parts of South-East Asia it is the most common malignant neoplasm and accounts for around a third of all cancers. Furthermore, the incidence rates for large countries, such as India and the USA, conceal regional and ethnic variations. For example, incidence rates tend to be higher in urban as opposed to rural communities, and in the USA are higher for blacks than whites. In the United Kingdom, inci¬dence rates are slightly higher in Scotland than in England and Wales. In the United Kingdom the incidence of oral cancer is 9 per 100,000 of the population, which represents around 6,800 new cases per annum. The disease is more common in men than in women; the male:female ratio is currently 2:1. Oral cancer incidence increases with age, and the majority of cases (greater than two-thirds) are diagnosed after the age of 50 years old; less than 5% occur in individuals below the age of 40 years old.
Does the hand that controls the cigarette packet rule the smoker? Findings from ethnographic interviews with smokers in Canada, Australia, the United Kingdom and the USA
