Oral leukoplakia developing on lichen planus: a case report of malignant transformation

Background: Oral potentially malignant disorders (OPMDs), such as oral leukoplakia and oral lichen planus, are associated with an increased risk of malignant transformation to oral squamous cell carcinoma. The estimated malignant transformation rate for leukoplakia ranges from 6.64% to 9.5%, while oral lichen planus carries a lower but significant risk (0.7%–1.4%). Current decision trees, such as that proposed by van der Waal, recommend excision for dysplastic leukoplakia but are less clear for non-dysplastic lesions, particularly in the presence of additional risk factors. This case report highlights the importance of a risk-stratified approach in the management of OPMDs, emphasizing the need for early intervention in high-risk patients to prevent delayed cancer diagnosis. Case Presentation: A 73-year-old male, with a history of 19 pack-years of smoking (quit in 1984) and bilateral oral lichen planus, was referred for evaluation of asymptomatic white reticular lesions on the buccal mucosa. After 1 year of follow-up, a new homogeneous, asymptomatic white keratotic plaque appeared on the left lateral border of the tongue. Biopsy confirmed leukoplakia superimposed on oral lichen planus. Despite the absence of dysplasia on initial biopsy, the lesion was excised due to its high-risk location and the patient’s cumulative risk factors (size >200 mm², tongue location). Histopathological analysis of the excised specimen revealed an in situ squamous cell carcinoma (cT1N0M0). The patient underwent partial glossectomy with clear margins. At the 1-year postoperative follow-up, he exhibited a mature linear scar with no signs of recurrence and preserved tongue mobility, demonstrating minimal functional sequelae. Conclusions: This case underscores the importance of considering cumulative risk factors—such as lesion size, location, and the presence of multiple OPMDs—in the management of oral leukoplakia. We propose a modification to the van der Waal decision tree: excision of non-dysplastic leukoplakia in patients with ≥1 risk factor, rather than universal surveillance. Early surgical intervention in high-risk cases may facilitate the detection of carcinoma at earlier stages, improving patient outcomes and reducing the need for more invasive treatments. Further studies are needed to validate the inclusion of multiple OPMDs as an independent risk factor in clinical decision-making.