A clinical follow-up study of 327 patients with oral lichen planus is reported. The purpose of this investigation has been to estimate the incidence of malignant transformation of oral lichen planus. A reexamination was possible in 225 cases and the observation period varied from 1 month to 12 years (mean, 3.6; median, 2.9). Sixteen patients died and 45 patients did not appear at the follow-up examination. In 41 patients, the lesions disappeared. In one case, a carcinoma developed after an observation period of five years; consequently, the incidence of malignant transformation in this study was less than 1%. In two cases, oral lichen planus lesions were found to be present at the time oral cancer was diagnosed.
Fulling H. Cancer Development in Oral Lichen PlanusA Follow-Up Study of 327 Patients. Arch Dermatol. 1973;108(5):667-669. doi:10.1001/archderm.1973.01620260017005