Incidence of Cutaneous Squamous Cell Carcinoma and Carcinoma in Situ Continues to Increase

Clinical Summary: 

• Design/Population: This nationwide, population-based study analyzed first-time, histologically confirmed diagnoses of cutaneous squamous cell carcinoma, cutaneous squamous cell carcinoma in situ, and keratoacanthoma among adults in Denmark between 2005 and 2023.

• Key Outcomes: The incidence of cutaneous squamous cell carcinoma and cutaneous squamous cell carcinoma in situ increased steadily over the study period, while keratoacanthoma incidence declined. Incidence patterns varied by sex, age, and anatomical site, with notable differences in tumor distribution between male and female patients.

• Clinical Relevance: These findings highlight the increasing burden of keratinocyte neoplasms and support ongoing surveillance, prevention efforts, and risk stratification based on demographic and anatomic factors.

Results from a nationwide, population-based study demonstrated that the incidence of cutaneous squamous cell carcinoma and cutaneous squamous cell carcinoma in situ increased steadily over nearly two decades, highlighting the growing burden of keratinocyte neoplasms.

“Cutaneous squamous cell carcinoma, [cutaneous squamous cell carcinoma] in situ, and keratoacanthoma pose growing public health challenges, due to their associated morbidity, health care burden and costs,” stated Kristine Duffau, MD, Danish Cancer Institute, Copenhagen, Denmark, and coauthors. “However, many countries lack systematic registration of these extremely frequent keratinocyte neoplasms.” 

In this nationwide population-based study, investigators used data from the Danish Pathology Registry and Danish Cancer Registry to identify adults aged 20 years or older with a first-time diagnosis of cutaneous squamous cell carcinoma (n = 54,563), cutaneous squamous cell carcinoma in situ (n = 31,712), or keratoacanthoma (n = 23,512) between January 2005 and December 2023. Age-standardized incidence rates and estimated annual percentage changes were evaluated according to sex, age, and anatomical site.

The incidence of cutaneous squamous cell carcinoma increased by an estimated 2.6% annually among male patients and 3.1% annually among female patients, reaching age-standardized incidence rates of 131.6 and 77.7 per 100,000 person-years, respectively. Cutaneous squamous cell carcinoma in situ increased by 6.4% annually in male patients and 5.8% annually in female patients, while the incidence of keratoacanthoma declined over the study period.

Sex- and age-specific analyses demonstrated distinct patterns of disease distribution. Among patients with cutaneous squamous cell carcinoma or cutaneous squamous cell carcinoma in situ, lesions in male patients occurred more frequently on the face, scalp, and neck, whereas female patients more commonly presented with tumors of the lower extremities. Female patients aged 40 to 59 years also had higher incidence rates than male patients of the same age. Incidence trends for cutaneous squamous cell carcinoma and keratoacanthoma remained stable among adults younger than 50 years.

“Findings of this study have the potential to influence future surveillance activities and clinical care through attention to sex, age, and anatomical site," concluded Dr Duffau et al. 

Source: 

Duffau K, Baandrup L, Frederiksen K, et al. Incidence trends of cutaneous squamous cell carcinoma, carcinoma in situ, and keratoacanthoma by sex, age, and anatomical site. JAMA Dermatol. Published online: January 28, 2026. doi: 10.1001/jamadermatol.2025.5700