Epithelial dysplasia of the oral mucosa—Diagnostic problems and prognostic features

Many oral cancers are preceded by potentially malignant lesions, which may appear as white or red patches on the oral mucosa. In the absence of validated molecular markers, the histological grading of oral epithelial dysplasia remains the only determinant of potential malignant change. Grading is notoriously unreliable, with wide intra- and inter-observer variability. However, conformity may be achieved between pathologists using similar standards and some objective criteria can be used for diagnosing and grading dysplasia. Oral dysplasia is graded simply as mild, moderate or severe, by an evaluation of a combination of cytological and architectural changes in the oral epithelium. Mild epithelial dysplasia, shows relatively few cytological aberrations involving only the lower third of the epithelium, while at the other end of the scale, severe dysplasia may show significant cytological atypia extending into the involved upper third of the epithelium. At its worst, dysplasia involves the full thickness of the epithelium and may be designated carcinoma in situ. This review describes the clinical and histopathological features of oral epithelial dysplasia and guides the pathologist on diagnosis and key prognostic factors.