Precancer of the oral mucosa.

According to the WHO collaborating centre precancerous lesions and precance rous conditions have to be distinguished. Precancer Background: Erythroplak ia is the most dangerous precancerous lesion. It is rare, but may often rem ain undetected. It will transform into cancer within five years and therefo re, has to be excised in every case. Leukoplakias show malignant transforma tion in 3 - 45% of the cases. In spite of modern molecularbiological and im munohistochemical techniques the clinical appearance and the histological g rading of the dysplasia are still most important prognostic factors. Until 1992 every lesion showing signs of moderate and severe dysplasia was excise d in our department. Despite this treatment strategy 6.2% of the leukoplaki as (n = 161) transformed into cancer. Therefore, we recommend to remove eve ry lesion which does not disappear after eliminating the etiological factor s. Methods: Since 1992 168 leukoplakias were completely removed using the C O(2)Laser and underwent histological examination. Results: In 3% of these c ases a carcinoma was detected in the leukoplakia; 5% of the lesions recurre d. Precancerous condition: The most important precancerous condition, the o ral lichen planus is treated in cases of erosive lesions only or if the pat ient is suffering from the symptoms. Malignant transformation is seen in 1. 5% of the patients within 10 to 15 years, Histologically the oral lichen pl anus does not differ from the oral lichenoid reactions, lesions in contact with amalgam restorations mostly. In these cases a causative treatment with replacement of the amalgam is recommended.