Risk factors for limb melanomas compared with trunk melanomas in Queensland.

The objective of this study was to investigate the risk factors for melanoma on the arms and legs in comparison with well-known risk factors for trunk melanoma. The study was a population-based case-control study of 77 individuals with limb (25 arm; 52 leg) and 86 with trunk melanoma, who were representative of all the individuals newly-diagnosed with primary limb melanomas in Queensland during 1979-1980 and 232 controls. A single physician interviewed and examined all individuals and assessed complexion type, sun exposure history and other potential risk factors and clinical features. After multivariate analysis, the strongest risk factor for both limb and trunk melanomas was the presence of more than 10 naevi on the arm (odds ratio limb melanoma=41.4, 95% confidence interval 10.4-164), though on histology, a preexisting naevus was more strongly associated with trunk than limb melanoma (P<0.004). Associations with blonde/light brown hair, propensity to freckle and sunburn were similar for melanoma on both sites. A lifetime history of painful sunburns significantly raised the risk of trunk but not limb melanoma, whereas solar keratoses on the arm or face were more strongly associated with limb than with trunk melanoma (marginally significant, P(homogeneity)=0.056). High ambient solar ultraviolet radiation in adolescence was also a stronger risk factor for limb than for trunk melanoma. In conclusion, this population-based investigation into specific differences in causes of limb versus melanomas of other sites suggests that the risk factor profile is intermediate between the profiles for head/neck melanoma (mostly cumulative sun damage) and for trunk melanomas (most strongly related to naevi).