Squamous cell carcinoma from oral lichen planus: a case report of a lesion with 28 years of evolution.

Lichen planus (LP) is a relatively common mucocutaneous disease with autoimmune etiology. Considering its malignancy potential, it is important to define the correct diagnosis, treatment, and clinical follow-up for patients with LP so that the disease is not diagnosed late, thus hindering the chances of curing the disease. This study aims to describe a clinical case of oral squamous cell carcinoma, potentially originated from LP. The patient is undergoing clinical and histopathological follow-up. A 64-year-old Caucasian male patient presented with a proliferative verrucous lesion on the tongue and sought treatment at the School of Dentistry, University of Passo Fundo (UPF), Passo Fundo, Brazil. He claimed the lesion had been present since 1988, and had been initially diagnoses as "oral lichen planus." The physical exam presented three diagnostic hypotheses: plaque-like oral LP, verrucous carcinoma, and squamous cell carcinoma. After incisional biopsy and histopathological analysis, squamous cell carcinoma was diagnosed, probably originating from oral LP. The case study shows that malignancy from oral LP is possible, which justifies periodic clinical and histopathological follow-up, as well as the elimination of risk factors for carcinoma in patients with oral LP.