Potentially malignant lesions of the oral mucosa may be defined as lesions with an increased risk of progressing to squamous cell carcinoma. The most common lesions that are regarded as potentially malignant are leukoplakia and erythroplakia. The pathologists' role in the management of these lesions is to exclude a benign cause and to determine the degree of epithelial dysplasia, which remains the most accurate predictor of potential malignant change. Of all leukoplakias biopsy examined, however, only approximately 50% show dysplasia, and the estimated malignant transformation rate is only 0.1% to 2% per year. Overall, therefore, only approximately 5% of leukoplakias will become malignant, but those with histopathologic evidence of dysplasia show the highest risk.
In this article, we present a patient with a typical lesion of leukoplakia on the tongue, which showed epithelial dysplasia and progressed to squamous cell carcinoma. We summarize the clinical and histologic findings and discuss the role of histopathology in the diagnosis and management of these lesions.