Oral lichenoid tissue reactions: diagnosis and classification

The concept of lichenoid tissue reaction/interface dermatitis was introduced in dermatology to define a number of diverse inflammatory skin diseases linked together by the presence of common histopathological features. Similarly to the skin, the oral mucosa is affected by a variety of oral lichenoid lesions. Oral LTRs (OLTRs) include: oral lichen planus; oral lichenoid contact lesion; oral lichenoid drug reaction; oral lichenoid lesions of graft-versus-host disease; oral discoid lupus erythematosus; oral lesions of systemic lupus erythematosus; erythema multiforme; paraneoplastic pemphigus/paraneoplastic autoimmune multiorgan syndrome; chronic ulcerative stomatitis and lichen planus pemphigoid. Traditionally, diagnosis of OLTRs relies on clinical and histological correlation but in several instances this approach fails to provide a reliable diagnosis. Inclusion of molecular techniques may refine our ability to differentiate OLTRs.