The Lichenoid Tissue Reactions of the Oral Mucosa: Oral Lichen Planus and Other Lichenoid Lesions.

Lichenoid changes in the oral mucosa can be encountered in a wide range of lesions and can have varied etiologies. Immune-mediated disorders, including lichen planus, mucous membrane pemphigoid, discoid lupus erythematosus, and graft-versus-host disease, can have clinical and histologic overlaps. Lichenoid reactions to dental materials, such as amalgam, or to many systemic drugs are also well documented. Dysplasia of the oral cavity at times can also express a lichenoid histology, which may mask the potentially cancerous component. Proliferative verrucous leukoplakia, an unusual clinical disease, mimics oral lichen planus clinically and requires careful correlation of the clinical and pathologic features.