Lichen planus and malignancy. An epidemiologic study of 2071 patients and a review of the literature.

The literature contains 36 reports of squamous cell cancer associated with lichen planus, and several reports on increased frequency of oral cancer in patients with oral lichen planus. To examine the risk of malignant transformation, 2071 patients with lichen planus were followed up for an average of 9.9 years. Only eight squamous cell carcinomas were observed in this population after the first visit for lichen planus, producing a morbidity ratio of 1.0 (95% confidence interval, 0.9 to 1.2). Significant increase for oral cancer was observed in male subjects, with a morbidity ratio of 5.9 (95% confidence interval, 2.5 to 11.4). This study indicates that patients with cutaneous lichen planus do not carry an increased risk of malignant transformation of the skin lesions or internally; however, there is increased risk of oral cancer.