Background and objectives: It is generally accepted that cancer development in the oral mucosa may be preceded by an identifiable but as yet non-invasive precursor lesions. The aim of this study is a follow-up study based in a southern Taiwanese hospital to estimate the malignant transformation and duration in patients with potentially malignant oral mucosal disorders.

Methods: A total of 5071 patients between the first of January, 2001 and the end of December, 2010 with histological diagnoses of the oral premalignant lesions were fulfilled in the present study.

Results: The average age of onset of the initial diagnosis was 48.87years (range, 15–96 years). Overall approximately 4.32% of the potentially malignant oral epithelial lesions in this study progressed to oral cancer and the duration of transformation to malignancy was 33.6 months. These 219 patients were dysplasia with submucous fibrosis, 9/186 (4.84%); dysplasia with hyperkeratosis/epithelial hyperplasia, 63/957 (6.58%); submucous fibrosis, 37/994 (3.72%); lichen planus, 2/381 (0.52%); verrucous hyperplasia, 59/869 (6.79%); hyperkeratosis/epithelial hyperplasia, 49/1684 (2.91%). The transformation rate is 0.0689 (Kaplan–Meieier estimates).

Conclusions: Rate and duration of malignant transformation have been established in a population of Taiwan Chinese with a spectrum of potentially malignant oral lesions.