A rare case of isolated erosive ulcerative lichen planus of the vermilion zone

Unlike oral lichen planus (LP), isolated LP of the vermilion zone is a rare disease. It has a higher risk of malignization compared to other LP types, especially with the long course of the disease, which is to be related to frequent injuries and insolation of the area. In its turn, erosive/ulcerative form of LP under adverse circumstances (smoking, external irritants, immunosuppression, etc.) may antedate leukoplakia or transform into cancer; this clinical type of oral LP is difficult to differentiate from invasive squamous cancer. We describe a  clinical case of isolated erosive LP of the vermilion of the lower lip, long lasting and resistant to therapy. Due to persisting erosion on the lip, we performed an assessment by immunohistochemistry and histology to exclude squamous cell carcinoma. After the malignancy had been excluded and the diagnosis has been made, the patient was administered the treatment with aromatic retinoid acitretin, which was effective and led to complete epithelialization of the lesion. In patients with a long lasting, persistent LP of the vermilion, diagnostic biopsy should be performed to exclude malignization before administration of treatment.