- Design
- Nationwide register-based retrospective cohort
- Population
- 35,845 people with incident lichen planus in Denmark, 1978–2020
- Primary outcome
- Incident cancer vs general population (SIR)
- Effect
- Oral cavity SIR 7.5 (6.4–8.9) in women; 20-year absolute risk about 0.8–1.0%
This Danish nationwide cohort followed 35,845 people diagnosed with lichen planus between 1978 and 2020, with no prior cancer, and compared their cancer rates with the general population.
Women with lichen planus had markedly higher rates of cancer of the oral cavity (SIR 7.5, 95% CI 6.4–8.9), tongue (6.8) and lip (6.0), and of vulvar cancer (2.6); cutaneous squamous cell carcinoma was slightly raised (1.4). Men showed a similar pattern. Risks were highest at the site of the lichen planus: oral cancers after oral disease, genital cancers after genital disease. Absolute 20-year risks remained low — about 0.8–1.0% for oral cavity cancer and 0.2–0.4% for genital cancer.
This is observational and cannot show that surveillance changes outcomes, but the site-specific pattern is consistent and the cancers are ones that examination can find early. It supports making mouth and genital examination part of lichen planus follow-up, particularly for oral and vulval disease.
- Examine the mouth at every lichen planus review, even when the presenting disease is cutaneous.
- Ask about and, with consent, examine genital skin; vulvar lichen planus needs long-term follow-up.
- Explain that the absolute cancer risk is low — around 1% over 20 years for oral cavity cancer.
- Advise stopping tobacco and betel quid, which add to oral cancer risk.
- Share follow-up with dentists or oral medicine for patients with oral disease.
Why it matters
Lichen planus is often discharged once the skin settles, yet the cancer risk lies at mucosal sites that may never be examined.
Don't overread it
The study shows association, not that surveillance prevents cancer deaths.
The statistics, in plain English
A standardised incidence ratio of 7.5 means about seven and a half times the expected number of oral cavity cancers. Because the starting risk is low, that still translates to around 1 in 100 over 20 years.
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