Population-based incidence of vulvar and vaginal melanoma in various races and ethnic groups with comparisons to other site-specific melanomas.

Little is known on the difference in the incidence of vulvar and vaginal melanomas in various racial/ethnic groups. Population-based incidence of these melanomas in Asian and Hispanic individuals is almost unknown. Using 1992-2005 data provided by the National Cancer Institute's Surveillance, Epidemiology, and End Results Program, we calculated age-adjusted incidence rates of vulvar and vaginal melanomas in various racial/ethnic groups. From 1992 to 2005, there were 324 vulvar melanomas and 125 vaginal melanomas diagnosed in this group. The annual age-adjusted incidence rates (per million female population) of vulvar and vaginal melanomas in the different racial/ethnic groups was 0.87 (Blacks), 0.75 (American-Indian), 1.03 (Asians and Pacific Islanders), 1.22 (Hispanics), and 1.90 (non-Hispanic Whites). The overall white/black incidence ratio in vulvar and vaginal melanomas was 3.14 : 1 and 1.02 : 1, respectively; which is much less than that of cutaneous melanoma (13 : 1-17 : 1) and uveal melanoma (18 : 1) and is similar to that of conjunctival melanoma (2.6 : 1) and other mucosal melanomas (2.1 : 1-2.3 : 1). The low racial difference in vulvar and vaginal melanomas (as well as conjunctival and other mucosal melanomas) may be determined by their microenvironment factors (all originate from mucosa or semi-mucosa tissues). The incidence of vulvar and vaginal melanomas has does not increased in recent decades or toward the south (more sun exposure), indicating that ultraviolet radiation is not a causative factor in these melanomas. The slight decrease of incidence of vulvar melanoma in dark pigmented individuals may be related to the biochemical protective effects of melanin (as an antioxidant) rather than their photo-screen effects.