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Melanoma is the most feared and one of the most potentially lethal of cancers. The incidence of melanoma in the United States has risen sharply from a lifetime risk in 1981 of I in 250 to 1 in 100 today for melenoma. Melanoma presents as a changing or growing pigmented lesion, usually on the back in men and on the lower legs in women. Lentigo maligna melanoma is a more slowly growing form that appears as an irregular tan to brown macule on the head or neck of older patients. Black and Oriental patients may develop acral lentiginous melanoma, a macular melanoma of the palm, sole, or nail unit.

Most melanomas are flat to slightly raised, irregular pigmented lesions that slowly enlarge and develop different colors in the lesion. The "ABCDs" of melanoma describe its characteristics.

Color variegation is an early feature; shades of tan to brown to black, and red and white may be seen in the same lesion. As it enlarges, the lesion may become more irregular and may develop nodules. Most melanomas do not ulcerate or bleed unless advanced; occasionally, patients report that the lesions itch. Melanomas that appear as nodules are uncommon, and may represent metastases from an occult source. Amelanotic (unpigmented) melanomas occur, especially in very fair-skinned or red-haired individuals; these cancers may not be diagnosed.

Therapy. The treatment of primary melanoma is surgical excision. The risk of metastasis from melanoma is directly correlated with tumor thickness, which reflects the depth of invasion (see Table 4). The five-year survival of patients with in situ melanoma is almost 100%, but the risk of recurrence increases sharply.

In contrast to the wide margins used for melanoma in the past, current recommendations are 1 cm margins for thin melanomas ( 1 mm or less in thickness) and 2 cm margins for tumors 1-4 mm thick. Elective lymph node dissection is not indicated.

Many patients have moles that bear some of the features listed in Table 3. These moles, sometimes called dysplastic nevi, are evaluated on the basis of the history and the patient's risk factors for melanoma in addition to degree clinical atypia.

Diagnostic and therapeutic challenges. Benign nevi, seborrheic keratoses, actinic keratoses, basal cell carcinomas, and genital warts may all be pigmented; unless the diagnosis is certain, biopsy is indicated. Suspicious pigmented lesions should not be destroyed without a histologic confirmation of the diagnosis. Lesions suspected to be melanoma should be excised in torso.