Increased Risk of Squamous Cell Carcinoma of the Skin and Lymphoma Among 5,739 Patients with Bullous Pemphigoid: A Swedish Nationwide Cohort Study.

Evidence about the association of bullous pemphigoid and the risk of cancer is conflicting. Patients diagnosed with bullous pemphigoid (n = 5,739) between 2005 and 2016 were matched with a control cohort from the general population (n = 17,168) to estimate their overall and specific risk of cancer. The risk of squamous cell cancer of the skin (cSCC) was increased in patients with bullous pemphigoid (hazard ratio (HR) 1.3; 95% confidence interval (CI) 1.1-1.6). The risk of lymphoma within one year after bullous pemphigoid diagnosis was also increased (HR 3.1; 95% CI 1.3-7.6). While overall cancer risk prior to diagnosis of bullous pemphigoid was similar in cases and controls (prevalence odds ratio (POR) 1.0; 95% CI 0.9-1.0), the risk of male genital cancer within one year prior to diagnosis of bullous pemphigoid was lower in cases (POR 0.4; 95% CI 0.2-0.8). Clinicians must be aware of the increased risk of cSCC and lym-phoma in patients with bullous pemphigoid.