Relationship between epithelial dysplasia and the development of squamous cell carcinoma in oral leukoplakia

Objective: This study estimated the relationship between epithelial dysplasia and the development of squamous cell carcinoma in patients with oral leukoplakia. Patients and Methods: 199 consecutive patients (251 lesions) were followed up for more than 1 year between 1980 and 2000, with a mean follow up period of 6.3 years, Results: The occurrences of epithelial dysplasia and severe dysplasia were higher among patients with ulcerated or verrucous leukoplakias than among those with homogeneous or nodular leukoplakias (p < 0.05). The malignant transformation rate was 3.5% (7/199 patients). The mean transformation period was 3.1 years, ranging from 7 months to 13 years. There was an obvious relationship between the malignant transformation and the clinical types, especially with verrucous and ulcerated leukoplakia (p < 0.05). In addition, the malignant transformation rate was higher among patients with severe dysplasias than among those with mild or moderate dysplasias (p < 0.05). Conclusion: These results show the importance of long-term follow-up, even for patients with clinically and histopathologically innocuous leukoplakia and suggest that patients with verrucous or ulcerated leukoplakia with severe dysplasia are the most likely to develop squamous cell carcinoma from oral leukoplakia.