JAMA Dermatol. 2026 Jan 28. doi: 10.1001/jamadermatol.2025.5700. Online ahead of print.
ABSTRACT
IMPORTANCE: Cutaneous squamous cell carcinoma (cSCC), cSCC in situ (CIS), and keratoacanthoma (KA) pose growing public health challenges, due to their associated morbidity, health care burden and costs. However, many countries lack systematic registration of these extremely frequent keratinocyte neoplasms.
OBJECTIVE: To estimate incidence rates and trends of first-time, histologically confirmed cSCC, CIS, and KA in Denmark (2005-2023) by sex, age, and anatomical site.
DESIGN, SETTING, AND PARTICIPANTS: A nationwide, population-based study using data from the Danish Pathology Registry and Cancer Registry was conducted, including individuals 20 years or older receiving a first-time diagnosis of cSCC, CIS, or KA from January 1, 2005 to December 31, 2023. Data analyses were conducted from January to July 2025.
MAIN OUTCOMES AND MEASURES: Age-standardized incidence rates (ASIRs) as well as age-specific incidence rates per 100 000 person-years with corresponding estimated annual percentage changes (EAPCs) and 95% CIs were calculated.
RESULTS: A total of 109 787 histologically confirmed cases were identified in 95 352 unique individuals (55 891 male individuals [50.9%], 53 896 female individuals [49.1%]) 20 years or older in Denmark, receiving a first-time diagnosis of cSCC (n = 54 563), CIS (n = 31 712), or KA (n = 23 512). From 2005 to 2023, cSCC ASIRs increased (EAPC for male individuals, 2.6%; EAPC for female individuals, 3.1%), reaching 131.6 and 77.7 per 100 000 person-years in male individuals and female individuals, respectively. CIS increased markedly (EAPC, for male individuals, 6.4%; EAPC for female individuals, 5.8%), and KA declined. Stratified analyses showed distinct sex-specific anatomic patterns. Predilection sites for cSCC and CIS were the face, scalp, and neck, with particular predominance among male individuals. Female individuals exhibited higher ASIRs on the lower limbs compared with male individuals (male vs female individuals: cSCC, 7.63 vs 12.32 per 100 000; CIS, 6.21 vs 12.63 per 100 000; KA, 3.47 vs 7.20 per 100 000, respectively). KA primarily affected the extremities. Female individuals aged 40 to 59 years showed higher incidence rates than male individuals across all keratinocyte neoplasms (male vs female individuals: cSCC, 131.6 vs. 77.7 per 100 000; CIS, 89.4 vs. 78.6 per 100 000; KA 28.6 vs. 27.6 per 100 000, respectively). Trends among individuals younger than 50 years with cSCC and KA were stable.
CONCLUSIONS AND RELEVANCE: In this nationwide cohort study presenting the most comprehensive dataset of incident cSCC, CIS, and KA, with 109 787 histologically confirmed patient cases, covering nearly 2 decades and spanning across all Danish health care sectors, incidence of cSCC and CIS continued to rise, consequently affecting more people, and sex differences diminished. Stabilizing trends in individuals younger than 50 years may indicate early prevention effects. Findings of this study have the potential to influence future surveillance activities and clinical care through attention to sex, age, and anatomical site.
PMID:41604163 | DOI:10.1001/jamadermatol.2025.5700
