Oral Lichen Planus — SCE Dermatology MCQ

Correct answer: B — Approximately 0.5-1%

The correct answer is B, approximately 0.5-1 percent per year. Oral lichen planus (OLP) is classified by the WHO as a potentially malignant disorder, and large cohort and meta-analytic data consistently show a malignant transformation rate to oral squamous cell carcinoma of around 1 percent per year, which is the figure used in UK oral medicine and maxillofacial practice for counselling and surveillance planning. This risk applies across OLP subtypes but is higher in erosive and atrophic disease than in the reticular, Wickham striae pattern described in this patient. Because the risk is real but low, patients need long term dental and oral medicine follow-up with biopsy of any new ulceration, induration or persistent change, rather than routine excision or reassurance that no risk exists. This modest but non-negligible rate is what distinguishes OLP management from lichenoid reactions with uncertain risk and from benign, non-premalignant white lesions. Why the other options are wrong: A, 5-10 percent: this overstates the annual risk by roughly an order of magnitude and is not supported by cohort or meta-analytic data on OLP. C, no risk of malignant transformation: incorrect because OLP is formally recognised as a potentially malignant disorder, not a purely benign condition, which is why lifelong review is recommended. D, 15-20 percent: this figure is far higher than any reported transformation rate and would imply a risk closer to that of severe dysplasia or carcinoma in situ, which is not the case for OLP. E, over 25 percent: this is grossly inconsistent with published data and would mean most patients with OLP eventually develop cancer, which contradicts decades of follow-up studies. Key point: Oral lichen planus is a potentially malignant disorder with an annual malignant transformation rate of approximately 0.5-1 percent, mandating long term surveillance rather than reassurance or overestimation of risk.

Reference: British Journal of Oral and Maxillofacial Surgery (2023), 'Malignant transformation rate of erosive oral lichen planus: a retrospective study', UK cohort study confirming a malignant transformation rate of approximately 1% in oral lichen planus, https://www.bjoms.com/article/S0266-4356(23)00606-X/abstract