Melanoma predilection for the lower limbs of women

Abstract

There is a clear predilection for cutaneous melanomas to occur on the lower limbs in women that is not understood. To assess this phenomenon in more detail than previously, we examined the distribution of primary melanomas on the lower limbs of females vs. males on different subsites and across age groups. We conducted a records-based study at an oncology hospital in north-west England and collected information on age at diagnosis, sex and anatomical subsite (thigh, lower leg, foot) from case notes and pathology reports of an unselected sample of 1522 patients with primary invasive melanoma treated between 2002 and 2015. A χ2-test was used to assess differences between categories, and multinomial logistic regression to calculate odds ratios (ORs) with 95% confidence intervals (CIs) for melanomas on limb subsites by age group in females vs. males. Of 316 patients with primary melanomas of the lower limb, 227 (72%) were in females: 55 on the thigh (F:M = 1.83), 142 on the lower leg (female : male ratio 3.74) and 30 on the feet (female : male ratio 1.15). Females aged < 40 years had 20 times the odds of males of presenting with thigh vs. foot melanomas (OR 20.0, 95% CI 2.6–152.6) and 7.5 times the odds of males aged < 40 of presenting with lower leg melanoma (OR 7.5, 95% CI 1.1–49.2). After the age of 40 years, odds of females developing thigh vs. foot melanomas were similar to the odds in males (OR 0.8) but corresponding odds of lower leg melanoma in females vs. males remained significantly increased (ORs 4.2 at the age of 40–59 years; OR 2.8 at ≥ 60 years of age). Results suggest females and males have higher prevalence of both genetic and environmental risk factors for lower limb melanomas overall, and also that the relative influences of these factors vary with anatomical subsite and age.