[Malignant progression of oral leukoplakia]

The relation between oral leukoplakia and its malignant progression was clinicopathologically analysed by using the long-term follow-up cases treated in Cancer Institute Hospital, Tokyo, for 37 years (1950-1987). A total of 89 oral leukoplakia cases had been followed up for 11 years and 3 months on average, and the diagnosis of each case was histologically confirmed on biopsy. This series consisted of 56 male and 33 female patients. During the follow-up period, malignancy was found in 8 cases, at 5 years and 9 months on average after the diagnosis of leukoplakia. Among the cases being followed over 10 years, an incidence of malignant progression of benign leukoplakia was estimated as 10.25%. According to the size of leukoplakia, the lesions measuring over 1 cm in diameter showed higher risk for cancer development than the smaller ones. In the follow-up of leukoplakia, dysplasia was identified in 6 cases, and all of them were mild in degree. Moreover, cancer developed in 2 out of these 6 dysplasia cases.