[Oral precancerous conditions--an overview].

Precancerous conditions are defined as a generalized state associated with a significantly increased risk of cancer. For the oral and perioral region, sideropenic dysphagia, oral lichen planus (OLP), oral submucous fibrosis (OSF), syphilis, discoid lupus erythematosus, xeroderma pigmentosum as well as epidermolysis bullosa play a role as precancerous conditions. The number of published cases of oral or perioral malignant transformation for some of these diseases is small. In addition, carcinomas of the tongue and the oral cavity associated with syphilis are of historical interest, although publications in the 1990s still reported positive serology of syphilis and carcinomas of the tongue. OLP is still controversially discussed as to its premalignant nature. Transformation rates have been reported between 0% and 5.6%. Recent prospective studies have revealed that possibly oral lichenoid reactions (OLR) are more likely to form the basis of malignant transformation as compared to the classic OLP. The differentiation between OLP and OLR is difficult both from clinical and histopathological aspects. The second most important precancerous condition is oral submucous fibrosis, which is caused by betel quid chewing. OSF is most prevalent in South and Southeast Asia. The transformation rate is as high as 7.6% making OSF one of the most important precancerous conditions of the oral region.