The use of tobacco and alcohol are the two most important risk factors for cancer of the mouth. Smoking is the single most important risk factor for oral cancer. The use of tobacco and alcohol synergistically increase the risk of oral cancer. Although it has been suggested that chewing tobacco is a significant cause of oral cancer, epidemiological studies have shown that the risk is small when there are no other concurrent lit-tobacco habits (e.g. cigarettes).1 By contrast, the use of paan (areca nut and tobacco mixed with spices and soaked in an alkali solution) is significantly associated with the development of oral cancer. Although a number of other factors have been implicated in the development of oral cancer, such as various bacterial and viral infections, for most oral cancers to date, none have been conclusively proven. For cancer of the lip, the single most important risk factor is heavy exposure to ultraviolet rays of the sun (Figure 1).
Figure 1. An SCC of the lower lip presenting as an ulcer. Notice the lack of a defined vermillion border and edema consistent with the SCC arising in the setting of actinic cheilitis.