Cancer and oral lichen planus in a Swedish population.

Oral lichen planus (OLP) is generally regarded as a premalignant condition. The objective of the present study was to assess the number of oral malignant tumours in a retrospective analysis of 1028 patients (mean age=55 years; range=18-86; female, n=667; men, n=351) who between 1978 to end of 1993 were diagnosed with OLP at the Faculty of Odontology, Göteborg University, Sweden. Patients with malignant tumours were identified through the Swedish Cancer Registry at the National Board of Health and Welfare, which annually reports the incidence of malignant neoplasms in the Swedish population. The incidence of oral squamous cancer (OSCC), other malignant tumours and survival in the study group was compared to the Swedish population. The total time with OLP in the study group amounted to 7009 person years, with a mean follow up of 6.8 years (SD=4.9). The observed incidence of OSCC was higher than the expected incidence in the study group. The difference was statistically significant (P<0.001). No statistically significant difference was found for any other malignant tumours than OSCC. Also, no statistically significant difference could be identified in survival between study group and the population. The results from the present study gives further support to the concept of a small but increased risk for development of squamous cell carcinoma in patients with OLP.