Malignant potential of oral lichen planus: observations in 722 patients from India.

The malignant potential of oral lichen planus was assessed on the basis of observations in 722 patients found among 27,599 individuals examined in various epidemiologic studies in Kerala, Ernakulam district, India. Seven hundred and two patients with oral lichen planus were re-examined annually over a 10-year period with a mean observation period of 5.1 years. Most of the lesions (93%) were observed among tobacco users. Carcinoma developed in 3 (0.4%) patients with oral lichen planus. Clinically, all 3 had atrophic components in their lesions, and all were tobacco users. The relative risk of a lichen planus developing oral cancer compared to a tobacco user was estimated as 3.3. However, this relative risk was not significant. Histologically, 74% of the 94 biopsies from oral lichen planus showed epithelial atrophy. Two of the 3 in whom cancer developed also showed epithelial atrophy. It is felt that epithelial atrophy probably renders the mucosa more vulnerable to the carcinogenic action of tobacco. Although this study could not confirm the precancerous nature of this disease with a high degree of certainty, the disease did not appear to be innocuous either.