Abstract
Epithelial dysplasia was examined clinico-pathologically in 196 cases of oral leukoplakia according to WHO's criteria. Fifty-seven cases (29.1%) were found to have epithelial dysplasia. The tongue was the most prevalent site at which epithelial dysplasia occurred, that is 31 of 66 case (47.0%). In 12 tems of WHO's criteria for epithelial dysplasia, the items 2, 1, 12 and 4 which were reported to be important to evaluate the potentiality of malignant transformation, were frequently seen in that order. Malignant transformation occurred in 14 cases (7.1%) of oral leukoplakia, in which the tongue was the most frequent site of malignant transformation (12 cases). Of the 14 cases, 7 showed epithelial dysplasia before malignant transformation. The cases whose grade of epithelial dysplasia had increased with time had a tendency to develop into cancer. Thus attention should be paid to the existence and grade of epithelial dysplasia in the treatment of oral leukoplakia.
