Risk of Malignant Transformation in Patients With Oral Lichen Planus or Lichenoid Lesions: A Retrospective Study of 323 Patients With a Minimum of 5‐Year Follow‐Up

OBJECTIVE: To estimate the risk for oral squamous cell carcinoma (OSCC) among patients with oral lichen planus (OLP) or lichenoid lesions (OLL) and the possible risk factors. MATERIAL AND METHODS: Two hundred thirty-nine OLP and 84 OLL patients diagnosed between years 1982 and 2017 were followed up to December 2023, diagnosis of an OSCC, or death. Potential demographic and clinical risk factors were compared, and a Cox proportional-hazards model was used to investigate associations between time to OSCC onset and variables of interest. RESULTS: Six OLP patients (2.5%; three females), in a mean follow-up of 17.5 years, and six OLL patients (7.1%; three females), in a mean follow-up of 13.8 years, developed OSCC. The annual MT rate was 0.14% for OLP and 0.5% for OLL. The mean time for OSCC development from OLP diagnosis was 11.4 years and from OLL diagnosis 12 years. Four OLP patients (67%; two females) developed OSCC in the mobile tongue, while in OLL patients OSCCs occurred at various sites. A potential association was observed between floor-of-mouth lesions in OLP and gingival or extraoral LP involvement in OLL and increased OSCC risk. CONCLUSION: This study confirms that both OLP and OLL patients are at a long-term risk of OSCC, and the risk is higher for OLL patients. Site-specific lesions in OLP and OLL were linked to increased OSCC risk, warranting confirmation in larger studies.