[Precancerous condition of the mouth mucosa: lichen ruber planus].

We report the case history of a 60-year-old male caucasian with lichen ruber planus of the oral cavity. After having this condition for 5 years, a medium-grade differentiated squamous cell carcinoma developed on the same side. Since a history of tobacco and alcohol abuse was negative, the Lichen ruber planus was considered to be a precancerous lesion without any other concomitant condition.