Anatomical Locations of Keratinocyte Carcinomas Among United States Veterans Affairs Healthcare System Patients in Minnesota: A Cross-Sectional Study

Previous studies have demonstrated a higher prevalence of keratinocyte carcinomas (KC) on sun-exposed areas, particularly for squamous cell carcinoma (SCC) compared to basal cell carcinoma (BCC). Few studies in the United States (US) have compared the prevalence of BCC to SCC by anatomical location. The aim of this study was to determine the KC prevalence in a Midwestern US population standardised by relative tumour density (RTD) per anatomical area, which has not been previously reported in the US. Data was collected from Veterans Affairs' patients with biopsy-proven KCs from October 1999 to September 2020. KCs were divided into BCCs and SCCs. RTD was calculated by standardising frequency of occurrence in a location by body surface area. The proportion of BCCs to SCCs for each location was also analysed. A total of 31 663 KCs (17 776 BCCs and 13 887 SCCs) were identified in 10 933 patients, with the majority on the head and neck. BCCs were more likely overall on the trunk and upper arms than SCCs. SCCs were more common on the hands, forearms, genitals/perineum/perianal area, and ears. Both BCC and SCC occurred more frequently over sun-exposed areas when controlling for body surface area of the location. Higher proportions of BCCs were found on sun-protected areas when compared to SCCs. The relative preponderance of SCCs on the genitals/perineum/perianal area may be due to human papillomavirus.