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MELANOMA

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Pigmented lesions are among the most common findings on skin examination. The challenge is to distinguish cutaneous melanomas, which account for the overwhelming majority of deaths resulting from skin cancer, from the remainder, which are usually benign. Cutaneous melanoma can occur in adults of all ages, even young individuals, and people of all colors; its location on the skin and its distinct clinical features make it detectable at a time when complete surgical excision is possible. Examples of malignant and benign pigmented lesions are shown in Fig. 105-1.

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FIGURE 105-1

Atypical and malignant pigmented lesions. The most common melanoma is superficial spreading melanoma (not pictured). A. Acral lentiginous melanoma is the most common melanoma in blacks, Asians, and Hispanics and occurs as an enlarging hyperpigmented macule or plaque on the palms and soles. Lateral pigment diffusion is present. B. Nodular melanoma most commonly manifests as a rapidly growing, often ulcerated or crusted black nodule. C. Lentigo maligna melanoma occurs on sun-exposed skin as a large, hyperpigmented macule or plaque with irregular borders and variable pigmentation. D. Dysplastic nevi are irregularly pigmented and shaped nevomelanocytic lesions that may be associated with familial melanoma.

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EPIDEMIOLOGY

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Melanoma is an aggressive malignancy of melanocytes, pigment-producing cells that originate from the neural crest and migrate to the skin, meninges, mucous membranes, upper esophagus, and eyes. Melanocytes in each of these locations have the potential for malignant transformation. Cutaneous melanoma is predominantly a malignancy of white-skinned people (98% of cases), and the incidence correlates with latitude of residence, providing strong evidence for the role of sun exposure. Men are affected slightly more than women (1.3:1), and the median age at diagnosis is the late fifties. Dark-skinned populations (such as those of India and Puerto Rico), blacks, and East Asians also develop melanoma, albeit at rates 10–20 times lower than those in whites. Cutaneous melanomas in these populations are diagnosed more often at a higher stage, and patients tend to have worse outcomes. Furthermore, in nonwhite populations, there is a much higher frequency of acral (subungual, plantar, palmar) and mucosal melanomas. In 2014, more than 76,000 individuals in the United States were expected to develop melanoma, and approximately 9700 were expected to die. There will be nearly 50,000 annual deaths worldwide as a result of melanoma. Data from the Connecticut Tumor Registry support an unremitting increase in the incidence and mortality of melanoma. In the past 60 years, there have been 17-fold and 9-fold increases in incidence for men and women, respectively. In the same six decades, there has been a tripling of mortality rates for men and doubling for women. Mortality rates begin to rise at age 55, with the greatest increase in men age >65 years. Of particular concern is the increase in rates among women <40 years of age. Much of this increase is believed to be associated with a greater emphasis on tanned skin as a marker of beauty, the increased availability and use of indoor tanning beds, and exposure to intense ultraviolet (UV) light in childhood. These statistics highlight the need to promote prevention and early detection.

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RISK FACTORS

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