Oral lichenoid dysplasia and not oral lichen planus undergoes malignant transformation at high rates

Objectives: Oral potentially malignant disorders (OPMD) include a variety of mucosal lesions such as oral lichen planus (OLP), oral lichenoid lesions (OLL) and oral lichenoid dysplasia (OLD). Their rate of malignant transformation ranges from 0% to 34% and is dependent on OPMD type, lesion site and a range of risk factors. This study seeks to determine the proportion of oral lichenoid conditions that transform into oral squamous cell carcinoma (OSCC) in an Australian population. Methods: The study is a retrospective audit of patients from a private oral medicine clinic, diagnosed with OLP, OLL or OLD using clinical and histopathological data between 2006 and 2014. Patients were cross-matched with Cancer Registry data for OSCC, and the rate and time to malignant transformation determined. Results: OLP and OLL patients displayed a low risk of malignant transformation; 0.49% (1/206) for OLP and 0% (0/31) for OLL. In contrast, OLD patients, all of whom presented clinically as OLP, were at much higher risk with 6.81% (3/44) developing OSCC over an average time of 4.6 years (±2.4 SD). Rates of smoking and alcohol consumption were no higher in OLD patients compared to others. Conclusions: Compared with other oral lichenoid conditions, OLD lesions are at a particularly high risk of malignant transformation and should be managed based on the presence of dysplasia and not the lichenoid inflammatory infiltrate. OLP demonstrates a relatively low rate of malignant transformation. Diagnostic histopathology is important for discriminating OLP from OLD.