Malignant transformation rate of erosive oral lichen planus: a retrospective study.

Oral lichen planus (OLP) is a chronic inflammatory oral condition previously known to have a rate of malignant transformation of around 1%. Additionally, erosive lichen planus, a subtype of lichen planus, which is a known risk factor for malignant transformation, has previously been unquantified in a large cohort of patients. In a single unit observation between 2005 and 2021 we retrospectively assessed 1,920 patients who underwent histological analysis for suspected oral lichen planus, and followed the progression of their disease to assess the rate of malignant transformation. In total, 1.39% of OLP transformed to oral squamous cell carcinoma over an average of 5.8 years. However, we found that the transformation rate of erosive OLP into malignancy was 5.98% with an aggressive clinical pathway. To our knowledge the incidence of erosive OLP has not previously been quantified in a large cohort of patients. This retrospective study sheds light on, and raises warning signs about, the seriousness of this condition.