[Potentially malignant character of oral lichen planus and lichenoid lesions]

Many authors have reported the possible malignant transformation of oral lichen. The incidence of this event remains controversial. Many authors make a distinction between the "true" oral lichen planus (OLP) and lichenoid lesions (LL) according to the WHO clinical and histological classification. For these authors an increased risk of development of oral cancer could occur only on LL. Our aim was to check this hypothesis on a cohort followed for 10 years.

We included patients who were referred to our team for the first time between 1995 and 1997, still followed in 2010, with a histological diagnosis of buccal lichen planus. We classified lesions as OLP or LL according to the WHO clinical and histological classification: the two clinical criteria for OLP were a reticulated aspect and bilateral and symmetric lesions. Three histological criteria were necessary for the diagnosis: dense inflammatory infiltrate in the upper lamina propria, liquefaction degeneration of basal keratinocytes, and no signs of dysplasia. The final diagnosis was OLP, when all clinical ad histological criteria were met otherwise it was LL. We studied the patient's outcome between their first consultations and May 2010.

Thirty-two patients, whose data was available, met inclusion criteria. Eight were diagnosed with OLP and 24 with LL. The mean follow-up was 164 months [154-183]. No oral cancer was observed in the OLP group. Two patients in the LL group presented with oral cancer after 45 and 143 months of follow-up.

Malignant transformations were observed only in the LL group. Our results correlate with those of Van Der Meij et al. published in 2006. The strict use of the WHO diagnostic criteria seems to allow identifying patients at risk of developing oral cancer (LL) and others with only a benign course of this chronic oral mucosal disease. These results need to be confirmed by prospective multicentric studies.