Objectives Oral leukoplakia (OLK) is one of the most common oral potentially malignant lesions (OPMD) and is reported to undergo malignant transformation (MT) to oral squamous cell carcinoma (OSCC) at rates of between 0.13% and 34%. This study seeks to determine the proportion of OLK lesions that develop into OSCC in an Australian population and assess the risk factors associated with this transformation. Methods The study is a retrospective audit of patients from a private oral medicine clinic, diagnosed with OLK 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 were determined. Results Oral leukoplakia patients with histopathological confirmation of their lesions underwent MT at a rate of 1.49% (3/202), with an average time to MT (TMT) of 5.2 years. When patients without histopathological confirmation were assessed, the MT rate was slightly less (1.30%; 4.9 years TMT). Patients who transformed were more likely to be older females with a history of smoking and alcohol use, with OLK present on the tongue or floor of mouth. The rate of oral epithelial dysplasia (OED) in the transformed group was surprisingly low (one third). Conclusions Oral leukoplakia is at a moderate risk of malignant transformation which can be reduced by careful management. Current tools for identifying high‐risk OLK, including histopathological assessment of OED, may not capture all lesions that undergo MT and should be supplemented by unbiased molecular biomarkers.

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.