Risk Factors for Melanoma by Anatomic Site The British Journal of Dermatology

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• The authors analyzed data from 2617 first invasive melanomas (975 controls) from 2 population-based case–control studies in Australia and the UK. They found that the incidence of melanoma was highest on the trunk (35%) and lower limbs (34%) and was lower for the upper extremities (20%) and head and neck sites (11%). Men had a higher frequency of melanoma on the head and neck, whereas women more frequently had disease on the extremities. Melanomas occurred more often on the head and neck than on any other site in patients older than 70 years. Higher density of nevi was associated with higher odds for melanoma of all sites, but a stronger association was seen with many nevi and melanoma on the trunk and extremities. Very fair skin type was associated with melanoma on nontruncal locations.

• This study sheds light on the factors that affect the risk of developing melanoma and how they vary based on the anatomic site of the melanoma. These data support the dual-pathway hypothesis, which holds that truncal melanomas are more strongly related to nevi and intermittent sun exposure, while head and neck melanomas are more related to chronic sun exposure.

– Caroline K. Crabtree, MD

Abstract

BACKGROUND

Melanoma aetiology has been proposed to have two pathways, which are determined by naevi and type of sun exposure and related to the anatomical site where melanoma develops.

OBJECTIVES

We examined associations with melanoma by anatomical site for a comprehensive set of risk factors including pigmentary and naevus phenotypes, ultraviolet radiation exposure and polygenic risk.

METHODS

We analysed harmonized data from 2617 people with incident first invasive melanoma and 975 healthy controls recruited through two population-based case-control studies in Australia and the UK. Questionnaire data were collected by interview using a single protocol, and pathway-specific polygenic risk scores were derived from DNA samples. We estimated adjusted odds ratios using unconditional logistic regression that compared melanoma cases at each anatomical site with all controls.

RESULTS

When cases were compared with control participants, there were stronger associations for many naevi vs. no naevi for melanomas on the trunk, and upper and lower limbs than on the head and neck (P-heterogeneity < 0·001). Very fair skin (vs. olive/brown skin) was more weakly related to melanoma on the trunk than to melanomas at other sites (P-heterogeneity = 0·04). There was no significant difference by anatomical site for polygenic risk. Increased weekday sun exposure was positively associated with melanoma on the head and neck but not on other sites.

CONCLUSIONS

We found evidence of aetiological heterogeneity for melanoma, supporting the dual pathway hypothesis. These findings enhance understanding of risk factors for melanoma and can guide prevention and skin examination education and practices.

The British Journal of Dermatology

Risk Factors for Melanoma by Anatomical Site: An Evaluation of Aetiological Heterogeneity

Br J Dermatol 2020 Dec 03;[EPub Ahead of Print], R Laskar, A Ferreiro-Iglesias, DT Bishop, MM Iles, PA Kanetsky, BK Armstrong, MH Law, AM Goldstein, JF Aitken, GG Giles, Australian Melanoma Family Study Investigators; Leeds Case-Control Study Investigators; HA Robbins, AE Cust 

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Benjamin Hidalgo-Matlock
Skin Care Physicians of Costa Rica

Clinica Victoria en San Pedro: 4000-1054
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