Cancer Risk in Patients With Overall and Site-Specific Lichen Planus

Importance: The association between lichen planus (LP) and subsequent cancer risk, particularly by anatomical site, is not well established. Objective: To assess the association between any LP, and site-specific LP, and the subsequent risk of cancer compared to the general population. Design, Settings, and Participants: This was a retrospective cohort study using nationwide Danish register-based data of individuals with an incident LP diagnosis (1978-2020), with no prior cancer, identified through the National Patient Register (any LP) and the Danish Pathology Register (any LP and site-specific LP). Data were analyzed from August 20 to December 20, 2025. Exposures: Any diagnosis of LP independent of site, and LP at specific anatomical sites (oral, cutaneous, and genital). Main Outcomes and Measures: Participants were followed up for incident cancer outcomes until death, emigration, or December 31, 2023. Cancers were identified through the Danish Cancer Register. Standardized incidence ratios (SIRs) with 95% CIs were calculated separately for females and males, comparing cancer incidence in patients with LP to the general Danish female or male population. Results: A total of 35 845 patients with LP (21 650 females and 14 195 males) were included in the analysis. Compared to the general population, females with any LP had increased risk of oral cancers (lip, SIR = 6.0; 95% CI, 3.3-10.0; oral cavity, SIR = 7.5; 95% CI, 6.4-8.9; tongue, SIR = 6.8; 95% CI, 5.4-8.4) and vulvar cancer (SIR = 2.6; 95% CI, 2.0-3.4), while the risk of squamous cell carcinoma was slightly elevated (SIR = 1.4; 95% CI, 1.3-1.6). In contrast, lung cancer risk was decreased (SIR = 0.7; 95% CI, 0.6-0.8). Results were consistent across follow-up. The cancer risk pattern was similar in male patients with LP. Site-specific analyses showed the highest risk of oral cancers in patients with oral LP, and of genital cancer in patients with genital LP. The 20-year absolute risks in female and male patients were 0.8% (95% CI, 0.7%-1.0%) and 1.0% (95% CI, 0.8-1.2) for oral cavity cancers, 0.5% (95% CI, 0.4%-0.6%) and 0.6% (95% CI, 0.5%-0.8%) for tongue cancers, 0.1% (95% CI, 0%-0.1%) and 0.2% (95% CI, 0.1%-0.3%) for lip cancers, and 0.4% (95% CI, 0.2%-0.5%) and 0.2% (95% CI, 0.1%-0.2%) for genital cancers, respectively. Conclusions and Relevance: In this cohort study, LP was associated with markedly increased risks of oral and genital cancers, as well as a slightly increased risk of skin cancer, particularly at sites corresponding to the anatomical LP location. While the absolute risk is low, site-specific cancer should be considered a possible long-term complication of LP.