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Primary melanomas of the esophagus and anorectum: epidemiologic comparison with melanoma of the skin

The objective of this study was to use recently available data to describe the epidemiology of melanomas of the esophagus and the anorectum in contrast to melanoma of the skin. The methods used include descriptive epidemiology using cases reported to the Surveillance Epidemiology and End Results registry, 1973–2003. All rates were age adjusted. We found 46 759 cutaneous melanomas, 170 anorectal melanomas and 20 esophageal melanomas, corresponding to age-adjusted rates of 70.1, 0.27, and 0.03 per million population, respectively. Median age of patients with melanoma of the skin was less than those with melanoma of the anorectum or esophagus (55 years vs. 71 years and 69 years, respectively). Rates of melanoma of the skin were 1.5-fold higher for men than for women (87.1 vs. 58.1 per 106); in contrast, rates of anorectal melanoma were 1.6-fold higher for women than for men (0.324 vs. 0.199 per 106). Rates of cutaneous melanoma for whites were 13-fold higher than for blacks (80.6 vs. 6.1 per 106, P<0.001), whereas the rates of anorectal melanoma were 1.7-fold higher among whites than blacks (0.273 vs. 0.173 per 106). Comparing the period 1973–1987 with 1988–2003, the rate of cutaneous melanoma increased 1.4-fold (56.0–80.1 per 106), whereas the rate of anorectal melanoma similarly increased 1.8-fold (0.182 to 0.329 per 106).In conclusion, anorectal melanomas, and especially, esophageal melanomas remain rare malignancies. This is the first report where temporal trends in anorectal melanoma are following the increased incidence of cutaneous melanomas, but it is unclear whether immunohistochemical diagnostic practices have influenced this trend. As gastrointestinal melanomas represent melanocytic transformation in the absence of sunlight, their epidemiology may provide etiologic clues to alternative or systemic transformative factors also operant in cutaneous melanoma.