- Design
- Nationwide register-based retrospective cohort, Denmark
- Population
- 35,845 people with incident lichen planus, 1978 to 2020
- Primary outcome
- Site-specific cancer incidence vs general population
- Effect
- Oral cavity cancer SIR 7.5 (95% CI 6.4 to 8.9) in women; 20-year absolute risk about 0.8%
A Danish nationwide registry study followed 35,845 people diagnosed with lichen planus between 1978 and 2020, without previous cancer, until 2023, and compared their cancer rates with the general population. Pathology records allowed analysis by site: oral, cutaneous and genital.
Women with lichen planus had about seven times the expected rate of oral cavity cancer (SIR 7.5, 95% CI 6.4 to 8.9) and tongue cancer (6.8), six times for lip cancer, and about two and a half times for vulvar cancer (2.6). Skin squamous cell carcinoma was slightly raised (1.4). Men showed a similar pattern. The excess was greatest where the disease was: oral cancer in oral lichen planus, genital cancer in genital lichen planus. Lung cancer was less common than expected.
The absolute risks were low: over 20 years, about 0.8% to 1.0% for oral cavity cancer and 0.2% to 0.4% for genital cancer. So the message is not alarm but continuity: affected mucosa needs to be looked at over years, and someone needs to own that.
This was observational and cannot say whether surveillance reduces cancer deaths, but the site-specific pattern makes a practical case for long-term review of the affected area.
- Record the sites involved in every patient with lichen planus, including mouth and genitals.
- Examine affected oral and genital mucosa at follow-up, not just the skin.
- Biopsy a non-healing ulcer, thickened plaque or new lump on affected mucosa.
- Agree long-term follow-up with the dentist or gynaecologist where appropriate.
- Tell patients the absolute risk is low but that persistent changes at the site should be checked.
Why it matters
Lichen planus is a long-term follow-up condition at the sites it affects, not a rash to discharge.
Don't overread it
This shows an association with cancer, not that structured surveillance saves lives.
The statistics, in plain English
A standardised incidence ratio of 7.5 means about seven and a half times as many oral cavity cancers as expected for the population. Because those cancers are rare, the 20-year absolute risk was still around 1%.
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