Melanoma Epidemiology, Risk Factors, and Clinical Phenotypes

IntroductionMalignant melanoma is an aggressive malignancy responsible for nearly 60% of death from skin cancers.Recent advancements in the biology and molecular genetics of melanoma are accompanied by an improved appreciation of the roles of both intrinsic and extrinsic risk factors in their contribution to disease.This chapter reviews the epidemiology, risk factors, and clinical phenotypes of melanoma. Melanoma epidemiologyOver the past two decades we have observed increases in the incidence of malignant melanoma in the Caucasian population, while overall mortality rates have remained somewhat stable.The incidence and mortality of melanoma is considered in terms of geography and ethnicity using data from the United States and worldwide. U.S. melanoma epidemiologyMelanoma trends in the United States were examined using data from the Surveillance, Epidemiology, and End Results (SEER) Program, a National Cancer Institute program that collects cancer and survival data from approximately 26% of the U.S. population.The SEER data revealed an increase in age-adjusted incidence rates of melanoma, which more than doubled among females and nearly tripled among males between 1973 and 1997(Jemal et al., 2001)).After an additional 7 years of SEER data, it was found that among young adults (aged 15-39 years) there was an increase in melanoma incidence among young women, and the authors suggested a possible role of ultraviolet radiation exposure, as discussed in further detail below (Purdue et al., 2008).Melanoma incidence has increased at 3.1% per year, with increases in tumors of all subtypes and thicknesses, and non-significant increases in melanoma mortality (Linos et al., 2009).The median age of melanoma diagnosis is 60 years, with an age-adjusted incidence of 20.1 per 10,000 individuals, from 2003-2007 (SEER website, accessed 2011).There are differences in melanoma incidence and mortality dependent upon ethnicity.The SEER data shows the highest incidence among Caucasians (19.1 females and 29.7 males per 100,000), followed by Hispanics (4.7 females and 4.4 males per 100,000), American Indians/Alaska Natives, Asian/Pacific Islanders, and Blacks (1.0 females and 1.1 males per 100,000)(SEER website, accessed 2011).Incidence data are depicted in Figure 1.Among U.S. www.intechopen.comAdvances in Malignant Melanoma -Clinical and Research Perspectives 4 Hispanics and non-Hispanics from 2004-2006, it was noted that Hispanic melanoma patients had poorer prognostic characteristics (stage, tumor depth, and ulceration) at the time of diagnosis (Merrill et al., 2011).Comparing the same ethnic groups over different regions of the country, male Hispanic Floridian patients had a 20% higher and non-Hispanic black Floridian patients had a 60% higher incidence of melanoma compared to non-Florida patients of the same gender and ethnicity (Rouhani et al., 2010).The SEER data projected that, in 2010, there would be 68,130 new melanoma diagnoses and melanoma-related deaths among 8,700 men and women (SEER website, accessed 2011).The median age at death is 68 years, with the highest death rates among the U.S. Caucasian population (2.0 females and 4.5 males per 100,000), followed by American Indian/Alaska Natives, Hispanics, Blacks, and Asian/Pacific Islanders, from 2003-2007 (SEER website, accessed 2011)).Overall mortality is depicted in Figure 1.African American patients with melanoma have poor overall survival outcomes, which were not explained by external factors such as treatment discrepancies or socioeconomic status (Zell et al., 2008).One plausible contributor is the anatomic distribution of melanomas in patients of differing cutaneous pigmentation.Whereas melanomas are most likely to occur on typical cutaneous surfaces in Caucasians, they are proportionally more common (though of similar overall incidence) on acral (hairless) or mucosal surfaces among darkly pigmented individuals-surfaces commonly associated with thicker lesions at diagnosis.