Malignant potential of oral planus: A prospective pilot study

Background: Oral lichen planus (OLP) is a chronic inflammatory mucocutaneous disorder, occurring up to 1% to 2% of the general population over 15 years. In literature, the reported rates of transformation of the oral lichen planus (OLP) in oral squamous cell carcinoma (OSCC) are discordant, varying from 0.4% to 5%. This paper aimed to report the results of long-term prospective follow-up of a cohort of OLP patients about the prevalence of malignant transformation, relatively to the clinical forms and location of neoplastic events arising in oral mucosae affected by OLP. Methods: A study group of 327 Italian patients, 229 women and 98 men, diagnosed with OLP in accordance to World Health Organization diagnostic criteria, was observed up each four-monthly along periods ranging from 9 to 108 months (mean, 81.7 months) care of the Department of Oral Pathology and Medicine of the University of Milan, from March 2001 through May 2009. Patients having history of tobacco and alcohol use were excluded to distinguish between true malignant transformations and conventional carcinomas occurring in the mouths of patients who happen to have OLP. Clinic-histopathological data included, in addition to histomorphologic outcome, the data of first OLP diagnosis, of first occurrence of OSCC and primary site of malignancy. Results: In a mean time of 3.27 years from OLP diagnosis eight out of 327 patients, 5 females and 3 males (mean age 68.6 years females and 62 years males), developed an OSCC in mucosal areas with pre-existing OLP. Rate of malignant transformation, based on a mean follow-up of 81.7 months, was calculated at 0.36% per year. Histopathologically, six OSCCs (75%) were well-differentiated while two (25%) displayed a moderate degree of differentiation. The clinical forms that more frequently underwent malignant transformation were those characterized by prevalently erosive component (50%) and keratotic component (38%), while one patient (13%) displayed mixed lesions. As to that the intraoral location between our cases, the tongue appears to be the preferential site of primary neoplasia. Discussion: There are only three studies with prospective design and regular plane of patients recall. Two of these, (Silverman et al 1991, Holmstrup et al 1988) having a mean follow-up of 7.5 years, presented respectively an annual transformation rate at 0.31% and 0.22% per year, similar to our. A study with mean observation period of 2.65 years, (van der Meij et al 2003) calculated the percentage of annual transformation as 0.65% per year and all events of malignancy occurred in oral lichenoid lesions. Conclusions: The findings of our prospective pilot study on an Italian cohort of OLP patients add further evidences to consider OLP as actually precancerous lesion. Consequently, a long term four-monthly observation is mandatory to improve the early diagnosis process at initial micro-invasive neoplastic stage.