Objectives: The possible malignant transformation of oral lichen planus (OLP) is the subject of an ongoing and controversial discussion in the literature. The main criticism of studies on this subject relates to the lack of sufficient data to support the initial diagnosis of OLP in cases that finally developed into squamous cell carcinoma. We describe the possible premalignant character of OLP and oral lichenoid lesions (OLL) of a prospectively followed cohort of patients with detailed documentary data.
Study design: A study group of 173 patients, 62 patients diagnosed with OLP and 111 patients with OLL, according to revised, modified World Health Organization diagnostic criteria, was followed up from 6.6 to 72.0 months (mean, 31.9 months). The expected number of patients with oral cancer in the group of patients with OLP and in the group of patients with OLL was estimated by comparing the number of patients, their ages, sex, and the length of follow-up to annual incidence rates of oral cancer for the general Dutch population, to explore the possibility of coincidental carcinomas. The binomial test was used to determine whether the observed number of cases of cancer in the OLP group and the OLL group exceeded the expected numbers.
Results: Three of 173 patients (1.7%), 2 men and 1 woman, developed squamous cell carcinomas of the oral mucosa during follow-up. All malignant transformations occurred in the OLL group. The annual malignant transformation rate, based on a mean follow-up of 31.9 months, was calculated as 0.65% per year. A comparison of the expected against actual figures for the development of carcinomas revealed no increase in patients with OLP and a 219-fold increase in patients with OLL, with the latter not statistically significant, but with a P value of .083, suggesting at least a trend.
Conclusion: Our results give support to the hypothesis that patients with OLL have an increased risk of oral cancer, but this increased risk was not detected in our sample of patients with OLP. Before a final statement with regard to the premalignant character of OLP and OLL can be formulated, the present follow-up study should be prolonged and expanded with a larger number of patients. Until then, we advise that patients with OLP and OLL should undergo biannual follow-up examinations. Follow-up will be particularly important in patients with OLL who have atrophic/erosive/ulcerative lesions.