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Pigmented lesions are among the most common findings on skin examination. The challenge for the physician is to distinguish benign lesions from cutaneous melanomas and nonmelanoma skin cancers (NMSCs). Both melanoma and NMSC are increasing in frequency, and melanoma accounts for over half of the deaths resulting from skin cancer. 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, but the vast majority of melanomas arise in the skin, often permitting detection at a time when complete surgical excision leads to cure. Cutaneous melanoma can occur in people of all ages and all colors. Examples of malignant melanoma of the skin, mucosa, eye, and nail are shown in Fig. 76-1.
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RISK FACTORS AND EPIDEMIOLOGY
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The epidemiologic patterns seen in melanoma reflect the genetic and biologic features of melanocytes and their response to environmental ultraviolet radiation (UVR). Clinical features that confer an increased risk for melanoma include: (1) vulnerability to sun damage (light/red coloration of skin, hair, or eyes; photodamaged skin; history of exposure to natural or artificial UVR; prior history of skin cancers of any type); (2) abnormal growth of melanocytes (increased absolute number of nevi, increased size of nevi, or atypical features of moles such as multiple colors, speckles, or shapes); and (3) immunosuppression (innate, functional, or drug-induced). Table 76-1 summarizes melanoma risk factors and the relative risk associated with these factors.
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