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Location of basal cell carcinomas suggests complex association with sun exposure

Low distribution of tumors on hands and higher distribution on less sun-exposed areas suggest a complex association between sun exposure and basal cell carcinoma, according to study results published in JAMA Dermatology.

The researchers used the QSkin Sun and Health Study in Queensland, Australia to identify 2,374 patients who had been treated for skin cancers between Sept. 1, 2010, and Sept. 30, 2012. The cohort included 5,150 skin cancers, of which 3,846 were basal cell carcinomas. There were 1,346 men and 1,041 women with a mean age of 59.7 years.

Patients were analyzed for relative tumor density, a calculated ratio of the proportion of tumors at specific anatomical sites to the proportion of skin surface area at the site. Body sites and their respective skin surface percentage included head and/or neck (9%), trunk including shoulders (32%), upper limbs (19%) and lower limbs (40%).

The sites with the highest occurrence of basal cell carcinomas were the head and/or neck (40.2%) and the trunk (33.9%), while the highest occurrence of squamous cell carcinomas were the upper limbs (34.9%) and the head and/or neck (33.4%).

The relative tumor density on hands for squamous cell carcinoma was 2.7 (95% CI, 2.33-3.07) compared with 0.19 (95% CI, 0.13-0.25) for basal cell carcinoma. In contrast, the relative tumor density on the back and/or buttocks for basal cell carcinoma was 0.9 (95% CI, 0.84-0.96) compared with 0.1 for squamous cell carcinoma (95% CI, 0.07-0.14).

“The observations that [basal cell carcinomas] occur relatively infrequently on the hand but relatively frequently on body sites that are only intermittently exposed to UV radiation point to more complex associations with sun exposure,” the researchers wrote. “Understanding the etiology and pathogenesis of [basal cell carcinoma] may lead to new avenues for prevention and treatment.” – by Talitha Bennett

Disclosure: The researchers report no relevant financial disclosures.