[Precancer stages of the oral mucosa: a review]

According to the WHO collaborating centre precancerous lesions and precancerous conditions have to be distinguished. Precancer:

Erythroplakia is the most dangerous precancerous lesion. It is rare, but may often remain undetected. It will transform into cancer within five years and therefore, has to be excised in every case. Leukoplakias show malignant transformation in 3-45% of the cases. In spite of modern molecular biological and immunohistochemical techniques the clinical appearance and the histological grading of the dysplasia are still most important prognostic factors. Until 1992 every lesion showing signs of moderate and severe dysplasia was excised in our department. Despite this treatment strategy 6.2% of the leukoplakias (n = 161) transformed into cancer. Therefore, we recommend to remove every lesion which does not disappear after eliminating the etiological factors.

Since 1992 168 leukoplakias were completely removed using the CO2 Laser and underwent histological examination.

In 3% of these cases a carcinoma was detected in the leukoplakia; 5% of the lesions recurred. Precancerous condition: The most important precancerous condition, the oral lichen planus is treated in cases of erosive lesions only or if the patient is suffering from the symptoms. Malignant transformation is seen in 1.5% of the patients within 10 to 15 years. Histologically the oral lichen planus 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.