[Verrucous squamous cell carcinoma complicating hypertrophic lichen planus. Three case reports and review of the literature].

Lichen planus is a chronic mucocutaneous T-cell-mediated disease, whose cause is still unknown. The first case of lichen planus that transformed into squamous cell carcinoma was reported in 1903. We present three patients in whom squamous cell carcinomas were identified in chronic lichen planus. The world literature includes at least 91 cases, including our three cases. In an epidemiological study, no significant risk of transformation of cutaneous lichen planus into squamous cell carcinomas was found. In contrast, there is a significantly higher risk of malignant transformation in mucosal lichen planus, so that the WHO had graded mucosal lichen planus as a premalignant condition.