Geographic location may be a causal factor for the development of basal cell carcinoma (BCC), according to a study published in JAMA Dermatology.1

Researchers in California performed a spatial statistical analysis of 28,408 patients diagnosed with BCC in 2011 or 2012, adjusting for factors such as age, gender, and socioeconomic status. The study consisted only of Caucasians.

Of the 14 analyzed counties, cases of BCC per 100,000 people ranged from 661 to 1598. Contrasting with the other counties, eastern Sonoma and northern Napa were associated with a relative BCC risk of 1.12 (P = .006); east Contra Costa and west San Joaquin counties were associated with a relative risk of 1.40 (P < .001).

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The researchers concluded that within the population studied, geographic clusters were recorded with a “modestly” increased risk of BCC contraction.

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It was noted, however, that this research is intended to inform future research projects aiming to establish a causal network; while geographic-related risks are an important starting point, they cannot alone show the reasons that some people are at greater risk of BCC development than others.


  1. Ray T, Kulldorff M, Asgari MM. Geographic clusters of basal cell carcinoma in a northern California health plan population. JAMA Dermatol. 20 Jul 2016. doi:10.1001/jamadermatol.2016.2536 [Epub ahead of print]