What is Melanoma?
Melanoma is a type of cancer that forms in melanocytes. A melanocyte is a normal cell, found in the skin, which produces melanin. Of the many different types of melanoma, most are seen in the skin (this also includes nail beds, soles of the feet, and scalp), but can be found in the eye, anal canal, rectum, and vagina. In 2002 there will be an estimated 53,600 new cases of melanoma diagnosed in the United States, accounting for about 4% of all cancers (up from 47,700 cases in 2000). The number of new cases has steadily increased for 30 years, but researchers are unsure why.
Risk Factors for Melanoma
The risk factors for melanoma include:
- Fair skin or complexion. People with fair skin, light eyes, or those who have a tendency to freckle or burn easily are at higher risk. Melanoma rates are 20 times higher in Caucasians than in Blacks. The melanin in dark skinned people has been found to have a natural sun protection factor (SPF) and can filter twice as much ultraviolet light as that of a light skinned person. This protection, however, is not complete and melanoma can develop in dark skinned people. Melanoma is more commonly found on soles, palms, or nail beds in dark-skinned people.
- A history of sunburns and/or exposure to ultraviolet light (both sun and artificial UV light). A history of 3 or more sunburns, particularly blistering sunburns, before age 20, greatly increases risk. A history of severe sunburns in childhood and adolescence may actually double the risk of melanoma in adulthood.
- Multiple dark moles. Certain types of moles, called dysplastic nevi, are associated with a high incidence of melanoma. These moles are typically large (>5mm in diameter) and have uneven pigmentation and borders. A single dysplastic nevi is associated with a 2 fold increased risk, while 10 or more indicates a 12 fold increased risk of developing melanoma
- Older age. As we age, our years of sun exposure increase, and therefore the risk of melanoma increases
- A personal or family history of melanoma. Researchers have found that the risk of melanoma is 2.24 fold higher in people with a first-degree relative with the diagnosis, making an accurate family history important.
For many years, the tanning industry has promoted tanning salons as a safe alternative to natural sun, or a way to prevent sunburn. The tanning machines were said to produce only UVA rays, without producing UVB rays, which are responsible for most sunburns. However, researchers have learned that tanning beds do produce UVB rays in varying amounts, depending on the machine. They have also learned that UVA is not as safe as once thought; it has many biologic effects that can cause long-term skin damage. As for using tanning beds to prevent sunburn on a vacation, this too, is untrue. A visit to a tanning bed, followed by natural sun exposure causes a cumulative effect on skin cells and can cause an unexpected burn.
Preventing melanoma
The best way to prevent melanoma is to protect the skin from sun exposure (both natural and artificial). Avoid sun exposure between 10am and 4pm; wear protective clothing, including a hat, when in the sun; use a sunscreen with a sun protection factor (SPF) of 15 or greater, everyday, even in the winter. Sunscreen use is especially important for children due to the fact that sunburns during childhood greatly increase the risk of melanoma in adulthood. Consistent use of sunscreen has even shown the ability to reduce further skin damage in people with a history of extensive sun exposure.
Be aware of the shapes and coloring of any moles you already have. Melanoma most often develops from an existing mole, causing its appearance to change. Examine your skin routinely in a mirror, including your back, bottom of your feet, nail beds, and scalp. Look for changes in existing moles, or the development of new ones. Problematic moles have the ABCD characteristics. A is for asymmetry. If an asymmetric mole were divided in half, one side would not look like the other. B is for border irregularity. The border of the mole may appear blurry and uneven. C is for color. This can be a change in the color the mole has always been, the development of a black mole, or one with redness in it. D is for diameter. You should have a mole that has changed in size, particularly those greater than 5mm in diameter, checked by a physician. These rules are not set in stone, which is why you should be aware of your own moles, and report any changes in moles to a physician.
Screening Tests
The best screening is a skin examination. Your physician should examine your skin during routine physicals, but you should also examine your skin routinely at home. Because you see your skin everyday, you are most likely to notice any changes early on. Prognosis is best when lesions are found early, making skin examination very important.
The signs of melanoma
Melanoma usually presents as an irregular mole, with the ABCD characteristics described above. This can be a preexisting mole that has changed or a newly developed mole. More advanced lesions may have inflammation, oozing, crusting, itching, ulceration or bleeding.
Melanoma diagnosis
When melanoma is suspected, an excisional biopsy should be performed. This biopsy removes the lesion and the layers beneath it, allowing the depth of the lesion to be accurately determined. The depth of the lesion determines prognosis and treatment, so it is important for this to be accurate. This depth is described in two ways: Breslow thickness, which is the depth of invasion in millimeters, and Clark's level, which describes depth of invasion by the tissue it invades (levels I-V).
All patients should have a chest x-ray and liver function studies to assess for metastases. In patients with stages II-IV, further work up for metastases is needed, including CT scan of the head and abdomen, and lymph node dissection (with or without sentinel node biopsy).
The treatments for melanoma
Surgery is the mainstay of treatment for melanoma. When melanoma is diagnosed by a biopsy, the next step is to have a "wide excision". This surgical procedure removes an area of tissue around where the lesion was. The amount of tissue removed is based on the depth of the melanoma. If the melanoma is determined to be stage II or greater, a lymph node dissection is needed.
Stage IV disease has a poor prognosis, with only 13 percent of patients alive 5 years after the diagnosis. Results of treatment with chemotherapy have been discouraging, but doctors continue to look for new combinations of therapies. In some instances, patients with isolated areas of metastasis are able to have these surgically removed, prolonging their lives.
Clinical trials are testing many agents including vaccines made from the patient?s own tumor cells, varying combinations of chemotherapy and immunotherapy agents, and surgical techniques. New medications and techniques are continually being tested to find more effective therapies for this disease.
Follow-up testing
About 5 percent of patients will develop a second melanoma in their lifetime, others may develop metastases from the original tumor, and therefore all require follow-up. Patients should be evaluated every 3 to 6 months for 3 years, then every 6 to 12 months for 2 years, then annually. Chest x-ray and liver function tests may be done each year, and CT scans as determined by the particular case.
For Further Information :
• The American Cancer Society. www.cancer.org
• OncoLink, The Abramson Cancer Center of the University of Pennsylvania. www.oncolink.org . The site includes a list of Internet-wide e-mail discussion groups (also called "listservers") which relate to various areas of cancer.
Dolores C.