Oral lichenoid contact reactions may occasionally transform into malignancy.

The purpose was to identify cases of squamous cell carcinoma (SCC) of the tongue, in which a biopsy taken at the site preceding the cancer could be verified to show a lichenoid contact type of reaction (LCR). We retrieved all 724 SCC of the tongue from the Swedish Cancer Registry in the period 1995-2000. These cases were cross-searched with our own oral biopsy data files from 1988 to 1994, in order to identify biopsies with LCR-type lesions preceding the cancer. We found four verified and some additional tentative cases. The study demonstrated that there is a low incidence of malignant transformation in LCR-type oral lesions, not much different from what has been previously reported in oral lichen planus.