Background:The purpose of pharmacovigilance (drug safety) is collection, detection, assessment, monitoring, and prevention of adverse effects with pharmaceutical products. It is meant to identify, characterize, prevent, or minimize actual or potential risks relating to medicinal products. To prevent these adverse effects and improve our practice, health professionals have a duty to report side effects to assess this risk and evaluate the benefit/risk requirements. Mitotane (Lysodren) is used for treating adrenocortical carcinoma. Currently, no side effects concerning oral and genital mucosa have been reported.Case Summary:This case report is about a 50 years old woman. Six months after the initiation on mitotane treatment, she developed erosive lesions located on the oral and vaginal mucosa. These drug reactions were diagnosed as erosive lichen planus by the biopsy. This lichenoid lesions were resistant to the usual treatments, mitotane being at the time not replaceable.Conclusion:This case describes an unreported adverse effect of mitotane, it is – to our knowledge – the 1st description of erosive lichenoid drug reaction due to Mitotane.