Oral lichen planus (OLP) is a T-cell-mediated chronic inflammatory disease of the oral mucosa. It has been considered by many authors as a premalignant condition. In some reported cases, there is lack of clinical and histological data leading to a wrong estimation of its malignant potential. We report the case of a 74-year-old woman who had been diagnosed with erosive OLP extending over gingiva, labial and buccal mucosa with absence of known exogenous carcinogens. Six years after, verrucous lesion appeared on labial lesion. Topical antifungal treatment was initially prescribed to treat a deep candida infection. Then, a biopsy confirmed the diagnosis of squamous cell carcinoma. Radiological examination confirmed absence of lymph nodes or metastatic lesion. Total surgical excision was performed with respect of carcinologic resection margins. Neither local recurrence nor second primary tumor was noted during 5 years of follow-up. The present case supports the view that OLP may undergo malignant transformation, and that this does not require exogenous carcinogens. It highlights the necessity of correct record of clinical, histological and treatment details to make possible and reliable the diagnosis of OLP malignant transformation. There is still a need of close follow-up of OLP and lichenoid lesion patients especially when having associated other carcinogenic risk factors.