Melanoma is a serious form of skin cancer, and the survival rate of melanoma is dependent on the stage of the disease at diagnosis (Table 17-1). Melanoma arises from melanocytes located at the epidermal and dermal layers of the skin and the choroids of the eyes. Melanocytes help synthesize melanin, a brown pigment which makes skin tan or brown and protects deeper layers of tissues from ultraviolet radiation damage (eg, sun damage). Melanoma is a result of malignant skin transformation from skin melanocytes or preexisting nevocellular nevi (moles). Although the etiology of melanoma is not fully understood, many risk factors have been identified. Risk for melanoma includes personal or family history of melanoma, presence of multiple atypical moles or dysplastic nevi, previous history of nonmelanoma skin cancer (eg, basal cell and squamous cell), and immunosuppression. Incidence of melanoma increases with intermittent intense ultraviolet sun exposure over chronic periods.
TABLE 17-1Stages of Melanoma and Mortality |Favorite Table|Download (.pdf) TABLE 17-1Stages of Melanoma and Mortality
|• Early stage—Localized diseasea |
| • Primary tumors ≤1 mm in thickness |
| • 5-y survival >90% |
| • Primary tumors >1 mm in thickness |
| • 5-y survival rate 50%-90% |
|• Advanced disease |
| • Disease with nodal involvement |
| • 5-y survival rate 20%-70% |
| • Distant metastasesb |
| • 5-y survival rate <10% |
Normal nevi present as evenly colored brown, tan, or black spots on the skin. They are round or oval in shape, and appear flat or raised. Nevi are generally less than 6 mm in diameter and stay about the same size, shape, and color. However, any nevi that change size, shape, or color are suspicious and require evaluation by a dermatologist. The ABCDE rule of melanoma is a useful tool to identify suspicious lesions. A is asymmetry where one-half of the mole does not match the other half; B is border irregularity where the edges of the mole are often irregular, blurred, ragged, or notched; C is color where the color of the mole is not uniform, it may appear with different shades of tan or blue-black, and sometimes mixed with colors of red, purple, and white; D is diameter where lesions are often greater than 6 mm in diameter, although melanoma can sometimes present with lesions of less than 6 mm in diameter; E is evolving or changing characteristics of a lesion.
Classification of Melanoma
Depending on the location and presentation of the lesions, the classification of melanoma can be different. Superficial spreading melanoma is the most common type of melanoma. The lesions arise from a preexisting flat nevus that develops into an irregular and asymmetrical nevus. Nodular melanoma is the second most common type of melanoma. Nodular melanoma has an aggressive and rapid growth pattern. The lesions are uniform in color and are ...