Melanoma

Melanoma is the most lethal of the cutaneous malignancies, causing more than 77% of skin cancer deaths. In the United States, more than 62,000 new cases of invasive melanoma and almost 50,000 new cases of melanoma in situ were diagnosed in 2008. Melanoma arises from the pigment-producing cells (melanocytes) located predominantly in the skin, but it also found in the eyes, ears, GI tract, leptomeninges, and oral and genital mucous membranes. Early detection and treatment of melanoma are the best means of reducing mortality.

The development of melanoma is not completely understood and is not as directly linked to chronic sun exposure as is BCC or SCC. Risk factors include fair complexion, red or blond hair, inability to tan or predisposed to burn, freckles, excessive childhood sun exposure, more than three blistering childhood sunburns, an increased number of moles (nevi) or dysplastic nevi, family history of melanoma, personal history of melanoma, immunosuppression, and older age.

One third of melanomas arise in a preexisting nevus. A changing or newly acquired nevus in a person over age 20 is the most common warning sign for melanoma. Increase in size, change in color, asymmetry of borders, and variegated pigmentation are signs that warrant a biopsy. The mnemonic ABCDE (asymmetry, border irregularity, color, diameter, evolving) is helpful to assess lesions that may be melano-cytic (Table 33-3). Symptoms such as bleeding, itching, ulceration, and pain in a pigmented lesion are less common but also warrant further evaluation.

The subtypes of melanoma include superficial spreading melanoma (60%-70%), nodular melanoma (15%-30%), lentigo malignant melanoma (5%-15%), and acral lentigi-nous melanoma (5%-10%). These are essentially histologic subtypes but do tend to favor certain areas or populations. Superficial spreading, the most common type usually occurs on the trunk or legs (Fig. 33-86). Lentigo maligna melanoma is an in-situ variant and usually found on the face in elderly persons (Fig. 33-87). Nodular melanomas often have a solid-black color, and their thickness predicts a worse prognosis (Fig. 33-88). Acral lentiginous melanoma is most often found on the great toe or thumb and is the most common type to occur in African Americans (Fig. 33-89).

Excisional biopsy, including 1 to 2 mm of normal skin surrounding the pigmented lesion, is optimal to provide

Table 33-3 Mnemonic for Signs and Symptoms of Melanoma

ABCDE

Description

Asymmetry

Half the mole does not match the other half.

Border irregularity

Edges of mole are ragged, blurred, or notched.

Color

Color over mole is not homogeneous; may be varying shades of tan, brown, or black; patches of red, blue, or white in some cases.

Diameter

Mole is larger than 6 mm.

Evolution

Previously stable mole that is changing (evolving) in color, size, or other signs or symptoms.

Figure 33-86 Superficial spreading melanoma on back. © Richard P. Jsatine.)
Figure 33-87 Lentigo maligna melanoma on the face. © The Skin Cancer Foundation.)
Figure 33-88 Nodular melanoma with 22-mm Breslow depth. © Richard P. Usatine.)

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Figure 33-89 Acral lentiginous melanoma on heel of African American woman. © Richard P. IJsatine.)

accurate diagnosis and histologic staging. Referral for biopsy may be appropriate based on the location and size of the lesion. "Scoop shave" biopsies can be performed as long as the depth of the specimen obtained is greater than 1 to 2 mm. This is important because the depth of tumor invasion (Breslow depth) is the most important prognostic indicator and used in staging. Melanomas are also staged based on presence of ulceration (histologically), lymph node involvement, and location of metastasis. Diagnosing melanoma early is critical to a good prognosis. Most thin tumors (Breslow depth <1 mm) have a greater than 90% 10-year survival rate.

Treatment for melanoma is primarily surgical and depends on the depth of the tumor. Lesions with Breslow thickness less than 1 mm can be excised with 1-cm margins. Lesions with Breslow thickness of 1 mm or greater should be referred for sentinel lymph node biopsy to provide accurate staging. There is limited adjuvant therapy for melanoma that has spread to the lymph nodes, and at this time there is no standard chemotherapy for metastatic melanoma. Clinical

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