The anatomical distribution of non-melanoma skin cancer: a retrospective cohort study of 22 303 Australian cases

Background: Non-melanoma skin cancers (NMSC) are the most common skin cancers worldwide with research establishing that ultraviolet (UV) radiation influences occurrence. However, recent studies about NMSC tumour frequencies suggested high NMSC predilections in low UV-exposed skin regions. Methods: The `Human Surface Anatomy Labeling System' was used to define 100 skin regions to map NMSC locations excised at Flinders Medical Centre (FMC) between 1 January 2012 and 31 December 2017. Data were retrieved from the FMC histopathology database. A customised phrase algorithm was used to run a systematic word search on the dataset to quantify NMSC locations. Results: A total of 22 303 NMSC excisions were identified; 80% were head and neck excisions. Scalp, periocular and nasal regions showed a significantly greater predilection for basal cell carcinomas (BCC). Squamous cell carcinomas (SCC) had significantly more excisions in lip, neck and scalp regions. Regarding gender-related variations, more males had BCC excisions in ear regions and more females had nasal, lip, and ankle excisions. In SCC excisions, more males had scalp excisions and more females had leg and lip excisions. Considering age-related variation, significantly higher proportions of BCC were found with forehead excisions compared to scalp, neck and lower limb regions for SCC, all being highest for 60-79-year age groups. Conclusion: The relationship between NMSC type and anatomical distribution may be partially explained by gender and age affecting NMSC predilections particularly in the head and neck. However, other skin regions could not be explained solely by these factors.