Oral Lichen Planus and Malignant Transformation: A Systematic Review

Objectives: Oral Lichen Planus (OLP) has been classified as a Potentially Malignant Disorder (PMD), nevertheless clinical and pathological diagnosis and its malignant transformation are still major points of debate. The aim of this study is to systematically review the literature to determine: 1) the malignant transformation risk of OLP, 2) the possible prognostic role of clinical and pathological features and 3) determine whether Oral Lichenoid Lesions (OLL) have a different malignant transformation rate.
Methods: PubMed, Scopus and Web of Science were used as search engines: only observational, full-length, English language studies were investigated. Inclusion criteria were: more than 50 patients, clinical and histological diagnosis; exclusion criteria were: case report, systematic reviews, diagnosis of lichenoid dysplasia, lichenoid drug or material reactions. PRISMA protocol was used to evaluate and present results. PROSPERO registration code is CRD42016048529.
Results: Among 2256 publication, only 40 were included in this review. A total of 15.429 patients (mean age of 54 years) were followed for a mean period of 80 months and developed 174 Oral Squamous Cell Cancer (OSCC), with an overall transformation rate (TR) of 1.12%, an annual TR of 0.17 and a monthly TR of 0.014. Being a female and having an erosive clinical presentation seem to slightly increase the transformation risk. No significant differences were detected when studies were divided according to WHO or van der Meij criteria.
Conclusions: This systematic review confirms that OLP may be considered a PMD and suggests that erosive type and females should be considered as risk factors. A strict clinical and pathological follow up should be considered for OLP patients. Major efforts should be done to establish strict clinical and histological criteria in the diagnosis of OLP and to perform more sound methodological observational studies.