A unique gender difference in early onset melanoma implies that in addition to ultraviolet light exposure other causative factors are important

Summary Using US SEER 17 R egistry data, age‐specific melanoma incidence rates were calculated and comparisons were made between males and females. Relative R isk ( RR ) for males and females in each age group was computed and compared with that from N ordic C ancer R egistry data set and to that for non‐melanoma skin cancer ( NMSC ). For age groups 44 and younger, females showed higher incidence rates, with a peak difference at age 20–24 ( RR  = 2.01, 95% CI  = 1.21–3.33). Males exhibited higher incidence rates after age 44. The same bimodal gender difference was confirmed by the N ordic C ancer R egistry data set, but it was not observed for NMSC , which is known to be strongly associated with cumulative exposure to solar UV radiation. We conclude that exposure to solar ultraviolet ( UV ) radiation is the major causative factor for melanoma at older age (>44 yr), but that other factors may play a role in early onset melanomas, particularly in females.