A comparison of the anatomic distribution of cutaneous melanoma in two populations with different levels of sunlight: the west of Scotland and Queensland, Australia 1982-2001.

To explore whether the anatomic distribution of melanoma differs with ambient sunlight levels, we compared age- and site-specific melanoma incidence in two genetically similar populations from different geographic regions. We ascertained all new cases of invasive cutaneous melanoma in the west of Scotland and Queensland 1982-2001. Melanoma incidence was calculated for four anatomic regions (head and neck, trunk, upper and lower limbs), standardized to the European population and adjusted for relative surface area of each site. Highest rates among males aged <40 years and 40-59 years were observed on the trunk, but on the upper limbs among Queensland females and lower limbs among Scottish females. After age 60, melanoma rates were highest on the head and neck in both sexes. In both sexes and at all ages, lower limb melanomas were more common in Scotland than expected from the Queensland population. These analyses indicate that while the overall distribution of melanoma is similar in populations with different levels of ambient sunlight, important differences remain. Identifying the causes of these differences is likely to provide better understanding of how sunlight causes melanoma.