Identification of differentiated dysplasia improves prediction of oral leukoplakia at increased risk of malignant progression

Oral leukoplakia is the most common potentially malignant disorder of the oral mucosa with a rate of malignant transformation into oral squamous cell carcinoma of 1-2% annually. The presence or absence of dysplasia as defined by the WHO is an important histological marker for malignant transformation risk assessment, but is not sufficiently accurate for patient stratification. We investigated whether identifying differentiated dysplasia contributes to oral leukoplakia malignant transformation risk assessment. We investigated whether classic or differentiated dysplasia were present in 84 oral leukoplakias. In 25 of these patients a squamous cell carcinoma developed during follow-up. Risk of malignant progression of oral leukoplakia increased from 3.3 (HR, p = 0.002) when only classic dysplasia was considered to 7.4 (HR, p = 0.001) when both classic and differentiated dysplasia were combined. This study demonstrates that identifying differentiated dysplasia as a separate type of dysplasia is important for the prognosis and stratification of patients with oral leukoplakia.