Clinicopathologic factors associated with malignant transformation of oral leukoplakias: a retrospective cohort study.

It is clinically challenging to identify oral leukoplakias that have a high risk of undergoing malignant transformation. The aim of this retrospective study was to elucidate the associations between malignant transformation of oral leukoplakias and various clinicopathologic factors. Patients with a diagnosis of clinical oral leukoplakia, verified through histopathologic examination and with access to digital images of the lesion, were retrospectively included for the period 2003-2013. Using the clinical images, all lesions were re-evaluated regarding diagnosis and clinical subtype. Of the 234 included patients, with a median follow-up of 9 years, 27 (11.5%) developed oral squamous cell carcinoma. Among the clinicopathologic factors investigated, non-homogeneous oral leukoplakia (OL), OL with dysplasia, and OL localized to the tongue showed statistically significant increased rates of malignant transformation in the multivariate Cox regression analysis. Non-homogeneous OL showed a 15.2-times higher transformation rate than homogenous OL (P<0.001). Dysplastic leukoplakias developed into carcinomas 2.4-times more often than did non-dysplastic leukoplakias (P=0.048). OL located on the tongue showed a 2.8-times higher malignant transformation rate than OLs at other oral locations (P=0.018), when other locations were combined into one group. Non-homogeneous OL, OL with dysplasia, and OL localized to the tongue have higher transformation rates.