Oral lichen planus: Malignant potential and diagnosis

Oral lichen planus (OLP) is one of the most common diseases of the oral mucosa. Clinically, it has specific and clearly identifiable features; bilateral symmetric presentation showing a lace-like network of fine white lines (known as Wickham's striae) is an essential element of OLP even if the lesion exhibits a mainly atrophic and erosive pattern. There are various lesions that resemble OLP clinically and histologically. These lesions are widely referred to as lichenoid reactions or lichenoid lesions (OLLs). OLLs include contact hypersensitivity to dental materials, drug-induced lichenoid lesions, lichenoid reactions in chronic graft-versus-host disease, and other lesions that resemble OLP. The risk of malignant transformation of OLP is the subject of ongoing debate in the literature. Some authors have suggested that only OLLs, but not OLP, are of a premalignant nature and thus, should be categorized as “other dysplastic conditions.” Contrary to this suggestion, many cases of oral squamous cell carcinoma (OSCC) developing in patients with OLP presenting with no epithelial dysplasia have been reported. In addition, it has been reported that multiple events including multifocal dysplasia and/or OSCC subsequently occurred in some patients with OLP, suggesting possible field cancerization in OLP. In this paper, differential diagnosis between OLP and OLLs and their malignant potential are reviewed.