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Pigmented lesions are among the most common findings on skin examination. The challenge for the physician 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 often permit detection at a time when complete surgical excision leads to cure. Examples of malignant and benign pigmented lesions are shown in Fig. 72-1.
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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, but the vast majority arise in the skin. Melanomas can also arise in the mucosa of the head and neck (nasal cavity, paranasal sinuses, and oral cavity), the gastrointestinal tract, the CNS, the female genital tract (vulva, vagina), and the uveal tract of the eye. 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. In 2016, >76,000 individuals in the United States were expected to develop melanoma, and ∼10,130 were expected to die. Mortality rates begin to rise at age 55, with the greatest increase in men age >65 years. Of particular concern is the increase in incidence among women <40 years of age, an increase 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. The latest Surveillance, Epidemiology and End Results (SEER) Registry data reveal that from 2004 to 2013, the rate of new melanoma cases has risen 1.4% each year, while death rates have remained stable. This is in the context of a 5-year relative survival improvement from 93.1% to 93.3% ...