Longitudinal studies in oral leukoplakias

Follow‐up examinations of 520 patients with oral leukoplakia during a 25‐ycar period showed cancer development in 31 cases, i.e. 5.9 %. The mean observation period was 8.7 years. The age distribution of leukoplakia showed that the highest frequency occurred in the age group 51–60 years; carcinoma was most frequency in the age group 61–70 years. Females had a higher prevalence for malignant transformation of oral leukoplakia (7.2 %). The tongue was the site of predilection for malignant transformation (in 38.8 % of the eases). Among etiological factors, smoking, mechanical irritation, alcohol consumption and electrical potential differences could be correlated with oral leukoplakia. Certain factors seemed to favor the development of cancer. Carcinoma originated in 26 % of verrucous leukoplakias and in 74 % of erosive leukoplakias. The highest risk for malignant transformation of leukoplakia occurs in the erosive type, whereby 28 % of all eases developed into cancer.