Problems and pitfalls in oral mucosal pathology

The oral mucosa is affected by a number of reactive, infective, inflammatory and immune-mediated disorders and distinguishing between them can be challenging. This review will concentrate on two histological patterns: the lichenoid tissue reaction and pseudoepitheliomatous hyperplasia. For each pattern the histological features are described, the differential diagnosis is discussed and the essential diagnostic features are given. Discussion on the lichenoid tissue reaction covers the entities of lichen planus, lichenoid reactions to drugs and dental materials, discoid lupus erythematosus, graft versus host disease and erythema multiforme, while that on pseudoepitheliomatous hyperplasia covers granular cell tumour, chronic hyperplastic candidosis, median rhomboid glossitis, necrotizing sialometaplasia and papillary hyperplasia of the palate.