The distinctive lower incidence rates of cutaneous melanoma on the hips and lower extremities of men

Abstract

Abstract Background Cutaneous melanomas (CM) are more frequently found on the trunk in men and on the hip and lower extremities (legs) in women. This discrepancy has been attributed to more UV exposure on women’s legs due to their dressing habits. Objective To understand the sex difference in the bodily distribution of melanoma, especially those on the legs. Methods CM incidences, relative tumor density, and tumor mutational burdens (TMBs) were compared among different body sites in different sex and race groups using the SEER data and the TCGA-SKCM data. This is a cancer registry-based cohort study. Results White men have lower rates and lower relative tumor density (RTD) of CM on their legs compared to the rest of their body sites, or to white females. Non-white men do not have such a trend. White women have comparable RTDs among different body sites. The race ratios are used to evaluate the approximate effect of sun exposure at different body sites, which further validates a distinct protective effect of men’s legs in melanoma. TMB on leg melanomas was lower as compared to other sites in both sexes. Conclusions legs of both sexes in whites show lower RTDs and lower levels of TMBs, suggesting a weaker association with UV exposure. Furthermore, white men are especially protected against CM on their legs, which suggests an unknown intrinsic protective factor as compared to women.