Epidemiology of oral precancer and cancer

Although a large number of lesions and conditions have been designated as premalignant, most of these diseases have a very low incidence. Furthermore, only a small percentage undergo malignant transformation. In this article, premalignant changes of the oral mucosa are described and contributory factors that enhance their malignant transformation are identified. The largest single risk factor is atrophy of the oral mucosa. Oral submucous fibrosis, tobacco use and iron deficiency anaemias enhance the risk of malignant transformation. The location of lesions is also considered, since certain sites display a greater predilection to malignant transformation. The epidemiology of oral squamous cell carcinoma among the South African populations is considered and compared with figures from other countries. The impact of urbanisation and changing habits have led to a gradual move towards equalization of the incidences for males and females. The tongue is the most commonly involved site in all South African racial groups. However, there are differences in site distribution. For instance, among whites there is a greater predilection for carcinoma of the floor of the mouth, while among blacks the palate is more frequently involved. The incidence is highest during the 7th decade.