Demographic and environmental factors associated with canine cutaneous squamous cell carcinoma development in...

Cutaneous squamous cell carcinoma (cSCC) is a common canine skin tumour that occurs more frequently in high ultraviolet (UV) environments. Despite Australia's consistently high UV exposure, large-scale epidemiological studies on canine cSCC are limited. This study investigates the frequency of canine cSCC in Australia, its geographic patterns relative to UV index, and its association with animal-level risk factors. A matched case-control study was conducted using records from the VetCompass database from 1st January 2014 to 31st December 2023. In total, 295 histopathologically confirmed cSCC cases and 1,180 matched controls were included. Frequency statistics of cSCC and animal-level risk factors associated with cSCC were analysed and spatial patterns were mapped. The highest proportions of cases were recorded in Queensland (39.7%) and New South Wales (39.3%), with increased frequency along coastal areas of both states. cSCC cases occurred most frequently on body regions caudal to the thorax (54.9%), in senior dogs (58.6%), in desexed males (45.1%), and in dogs with white mixed coat colour (43.7%). In the final multivariable model, senior (seven to 11 years old) and geriatric (12 + years old) dogs had significantly higher odds of cSCC than mature (two to six years old) dogs (odds ratio = 7.4 and 4.8, respectively; p ≤ 0.001). Risk was also markedly elevated in Dalmatians, bulldogs, Staffordshire terriers, and schnauzers compared with mixed breeds. Dogs with white or white mixed coats had higher odds of cSCC than dark-coated dogs (p ≤ 0.001). cSCC demonstrated anatomical and geographic patterns consistent with chronic UV exposure, with age, breed, and coat pigmentation emerging as risk factors.