Cancer, Skin (Melanoma)

Risk: Melanoma is most commonly diagnosed in those between 50 and 70 years of age, but the incidence in younger age groups is increasing. One in 4 cases now occur before age 40. Although women are only slightly more at risk than men, melanoma is the most common cancer in women between the ages of 25 and 29. Melanoma typically occurs in light-complected, blue-eyed, blond, or red-haired individuals of Scandinavian or Celtic extraction. It is rare in blacks, but when it does occur, it usually appears on the light-complected areas of the hands, feet, or mucous membranes. Exposure to some herbicides may also increase the risk for melanoma (Mayo Clinic Staff).

Superficial spreading melanoma occurs predominantly in Caucasions; nodular melanoma is seen most often in the 20- to 60-year age group; acral lentiginous melanoma and lentigo maligna melanoma are most common in the elderly ("Malignant Melanoma").

Incidence and Prevalence: In the US in 2001, there were 51,440 cases of melanoma. Of these individuals, 7,800 died (Berger 89). In the last 30 years, the percentage of new cases has more than doubled (Mayo Clinic Staff).

History: Typically, the individual will notice a change in the character or size of a mole or observe a suspicious new growth. Usually the patient is fair-skinned, has had episodes of sunburn at an early age, or has had repeated exposure to sun. In other cases, a close relative may have had melanoma, or the individual may be immunocompromised. If the melanoma has metastasized, symptoms may reflect the extent of the damage and organs affected.

Physical exam: The physical characteristics that distinguish moles from melanomas may not be readily apparent. The dermatologist follows the ABCD guidelines for clues: (A) asymmetrical growth; (B) borders notched or scalloped; (C) colors not consistent throughout the growth; and/or (D) diameter greater than 6 mm (¼ inch). In addition, the mole may become scaly or itchy or the pigment may have spread onto the adjacent skin. Very often, the individual notices that the mole has changed in texture or become hard or lumpy. The melanoma may present in a variety of shapes and colors: raised or flat; brown with black spots; raised with white, black or blue spots; or simply as black or gray lumps.

The doctor will give special attention to those areas potentially affected by malignant melanoma: the eyes are evaluated for ocular melanoma; the consistency and tenderness of superficial lymph nodes are documented; chest sounds may give clues to pulmonary metastasis; and abdominal palpation may reveal evidence of intraperitoneal metastasis.

Tests: The definitive test for melanoma is the skin biopsy. The surgeon will usually remove only the tumor and avoid disfiguring the surrounding skin. If the biopsy is negative, that will end the procedure. If the biopsy is positive, therapeutic steps will follow—including more invasive surgery, which will remove some healthy skin around the original site.

The physician may order other tests to gauge the level of possible metastasis and to evaluate related problems, including chest x-rays, blood tests, and various imaging studies such as MRI, CT scan, and PET scans. Special areas of interest are the liver, bones, and brain. Newer tests look at fundamental changes in the DNA. The reverse transcriptase–polymerase chain reaction (RT-PCR) assay identifies genetic alterations that reveal melanoma cells in the lymph nodes. This test confirms metastasis, allows appropriate treatment, and suggests the likelihood of recurrence. Other blood tests look for protein markers that point to the extent the melanoma has spread and may offer clues for treatment and prognosis.

The physician may order sentinel lymph node mapping (SLN) to determine the route of lymphatic drainage. A sentinal lymph node is the one most likely to be affected if the melanoma should spread. Mapping is performed by injecting a dye and a radioactive tracing agent into the tumor and following its course through the lymphatic system to the first lymph node it reaches. Lymph node mapping reaches a high degree of certainty when assisted by a nuclear medicine scan (lymphoscintigraphy). A biopsy is then taken from that lymph node. If the biopsy is negative, there is a reasonable assurance that other local lymph nodes are cancer-free.