Anatomic site, sun exposure, and risk of cutaneous melanoma.

PURPOSE: Sunlight is the principal environmental risk factor for cutaneous melanoma. A current hypothesis postulates that the role of sunlight in causing melanoma differs according to anatomic site. We tested this hypothesis in a population-based case-case comparative study of melanoma patients.
METHODS: Patients were sampled from the Queensland cancer registry in three groups: superficial spreading or nodular melanomas of the trunk (n = 154), of the head and neck (HN; n = 76), and lentigo maligna (LM) and lentigo maligna melanoma (LMM; for both LM and LMM, n = 76). Data were collected on school-age sun exposure and occupational and recreational sun exposure in adulthood. Odds ratios (OR) and 95% CIs were calculated using polytomous logistic regression.
RESULTS: HN melanoma patients were substantially more likely than trunk patients to have higher levels of sun exposure in adulthood (OR, 2.43; 95% CI, 0.98 to 5.99) and specifically, higher levels of occupational exposure (OR, 3.25; 95% CI, 1.32 to 8.00), but lower levels of recreational sun exposure (OR, 0.50; 95% CI, 0.21 to 1.19). LM and LMM patients reported higher occupational exposure and lower recreational sun exposure than trunk melanoma patients, although this was not significant. We found no significant differences between the groups for school-age sun exposures.
CONCLUSION: Melanomas developing at different body sites are associated with distinct patterns of sun exposure. Melanomas of the head and neck are associated with chronic patterns of sun exposure whereas trunk melanomas are associated with intermittent patterns of sun exposure, supporting the hypothesis that melanomas may arise through divergent causal pathways.