Malignant melanoma is the most life-threatening form of skin cancer, with 40,300 new cases expected to be diagnosed in 1997. Although malignant melanoma accounts for only 5% of reported skin cancer cases, it causes over 75% of skin-cancer-related deaths. By the year 2000, an American's lifetime risk of developing melanoma will be one in 75. Over the past two decades, the incidence of malignant melanoma in Caucasians increased at a faster rate than that of any other cancer, with the number of cases doubling. The incidence rate is rising most rapidly in persons below the age of 40, and the disease is now the most commonly occurring cancer in women between the ages of 25 and 29. The mortality rate for the disease has been increasing as well, with 7,300 melanoma related deaths now occurring a year.
Excessive exposure to the sun activates melanin, causing skin to darken or tan as a protective measure. Melanocytes are the cells in the skin that produce melanin, the pigment that gives skin color. But sun exposure can also transform melanocytes into cancer cells; these cells may rapidly multiply, resulting in melanoma. Melanomas can also form on areas of the body that are not exposed to the sun or are exposed only intermittently. If untreated, melanoma can spread or metastasize from the surface of the skin to internal organs.
There is no single reason why a person gets cancer, yet certain risk factors are associated with malignant melanoma. Excessive exposure to harmful ultraviolet-A (UVA) and ultraviolet-B (UVB) sun rays can increase a person's risk of melanoma. One or more blistering sunburns before age 20 can increase the risk of developing melanoma, and those who have fair skin and red or blond hair get melanoma more frequently than dark-skinned, dark-haired people. Although melanoma risk increases with age, 50% of melanoma cases occur in persons under age 50.
A family history of melanoma is another risk factor. About 10% of all melanoma patients have one or more family members with the disease. Certain moles, called atypical moles or dysplastic nevi, are more likely to become malignant than others, and an overabundance of these hereditary moles can also increase the risk of melanoma. Melanoma is nine times as likely to occur in people who have had a previous melanoma.
Although people cannot alter their genetic makeup or change their family history, there are things they can do to decrease their risk of getting skin cancer. Avoiding excessive exposure to the sun, especially during the height of the day (10:00 a.m. - 4:00 p.m.), wearing a sunscreen of Sun Protection Factor (SPF) 15 or above, visiting a dermatologist for routine check-ups and wearing long sleeves, and hats, and sunglasses are all ways to decrease the risk of getting skin cancer.
As with many other forms of cancer, the earlier that malignant melanoma is detected, the better. One can detect skin cancer early by conducting regular skin self-exams and noting any changes in moles or birthmarks on the surface of the skin. Any change in shape, size, color or symmetry, as well as any other irregularities, may indicate early stages of skin cancer. In addition to malignant melanoma, two other types of skin cancer exist: basal cell cancer and squamous cell cancer. Basal cell cancer accounts for 75% of skin cancer cases, and if treated, is usually curable. Approximately 20% of skin cancer cases are squamous cell cancer, in rare cases, it can spread to other body parts but is otherwise curable, as well.
Stages of Malignant Melanoma According to the American Joint Committee on Cancer's TMN staging system, there are four distinct classes of malignant melanoma, based on the thickness of the primary tumor (T), disease status of the lymph nodes (N) and whether or not the disease has metastasized (M). The four classes are:
Stage I -- Melanoma: Stage I is the most curable form of the disease. The malignancy is confined to one tumor on the highest level of the epidermis, with a tumor thickness less than 1.50 mm. The 5-year survival rate is greater than 90%.
Stage II -- Melanoma: Stage II is still confined to one primary tumor with a thickness of greater than 1.50 mm. The 5-year survival rate is greater than 60%.
Stage III -- Melanoma: Melanomas in this stage have nodal involvement. The 5-year survival rate is 13% to 38%.
Stage IV -- Melanoma: In this stage, the melanoma has metastasized to other organs. This is the most advanced stage of the disease. The 5-year survival rate is estimated at less than 10%.
Therapies for malignant melanoma include surgical excision of the melanoma, chemotherapy, radiation therapy and biological therapy, using interferons. Methods of treatment depend on the status of the disease or its clinical stage. When the melanoma has spread to internal organs, a combination of treatments can be used, often surgery coupled with chemotherapy and/or biological therapy.