Risk factors for melanoma by body site.

It has been hypothesized that cutaneous melanoma at different anatomic sites develops through divergent pathways. We examined this hypothesis prospectively. We followed 152,949 women and 25,204 men free of cancer at baseline for up to 14 years in three large prospective studies. We examined risk factors for melanoma by anatomic location (head or neck, trunk, upper extremity, and lower extremity). Polytomous logistic regression was used to test the difference among risk factors by location of melanoma. A total of 511 incident cases of invasive melanoma (49 head or neck, 188 trunk, 98 upper extremity, and 176 lower extremity) were included in the analysis. Compared with females, males had a higher risk of developing melanoma on the head or neck and trunk. History of severe and painful sunburn was most strongly related to melanoma of upper extremity; individuals with >10 burns had a 6.86-fold (95% confidence interval, 2.62-18.00) higher risk of melanoma of upper extremity compared with those with no burns (P for trend < 0.0001; P for difference by body site = 0.04). Number of moles was most strongly related to melanoma of the trunk; the multivariate relative risk for having >10 moles was 4.67 (95% confidence interval, 3.07-7.11) compared with having no moles (P for trend < 0.0001; P for difference by body site = 0.04). Age, family history of melanoma, and hair color did not statistically differ by anatomic site of the cancer. These data support divergent etiologic pathways of melanoma development by anatomic sites.