Malignant Transformation in Extraoral Lichen Planus: A Systematic Review and Meta-Analysis in the Context of the Risk in Oral Lichen Planus

Objectives: This systematic review aimed to evaluate malignant transformation (MT) in extraoral lichen planus to help contextualize the debated malignant potential of oral lichen planus in a mucocutaneous disease model. Methods: A comprehensive literature search was conducted across five databases and gray literature sources, without date restrictions. Observational studies reporting MT in cutaneous or genital LP were included. Data extraction, risk of bias assessment using Joanna Briggs Institute (JBI), and meta-analysis of proportions were performed. Subgroup analyses by anatomical site were conducted where possible. Results: Ten studies (15,829 patients) were included, with a predominance of women (93.1%). The pooled MT rate of extraoral LP was 1% (95% CI: 0.00–0.03). Subgroup analysis revealed a significantly higher rate in vulvar LP (2%; 95% CI: 0.02–0.03) compared to cutaneous LP (0%; 95% CI: 0.00–0.01) (p < 0.0001). Squamous cell carcinoma was the most frequent malignancy. The erosive and hypertrophic subtypes of LP were more commonly associated with cancer development. Conclusions: MT of extraoral LP appears to be rare, particularly in cutaneous forms. However, the risks observed in the genital mucosa reinforce the need for accurate diagnosis and long-term follow-up, especially in erosive presentations.