Skin Cancer: Malignant Melanoma

Diagnosis

Melanoma is suspected from the appearance of a lesion, but cells need to be examined microscopically to confirm the diagnosis. In addition, evaluation of nearby lymph nodes helps determine treatment and prognosis. A melanoma may start with an existing mole or birthmark, or from a site that was previously undistinguishable from the surrounding tissue. Seventy-five percent of such tumors then undergo progressive change over a period of six months to as long as many years, during which time the malignancy develops, but may not spread (metastasize) to other sites in the body. Because early detection greatly improves the outcome of a patient with melanoma, a primary care provider will check moles and other suspicious growths for changes indicating melanoma (e.g., sudden growth, changes in color or change to multiple colors, and irregular shape) during a routine physical examination. Individuals at risk for melanoma should ask their primary care provider to show them how to perform a self-examination. About half of melanomas are discovered through self-examination. People who are at high risk of developing the disease should consider yearly examinations by a dermatologist.

If melanoma is suspected, the patient's primary care provider may refer the patient to a dermatologist who is trained in recognizing the earliest signs of a melanoma lesion. The dermatologist will perform a biopsy on suspicious lesions. During a biopsy, the doctor removes the tissue suspected of containing a melanoma (often a mole and a bit of the skin around it), and examines the tissue under a microscope. Usually the entire lesion is removed for a biopsy, although it is also possible to just remove a portion of it for examination. A biopsy is typically an outpatient procedure, performed in the doctor's office with only a local anesthesia. If the physician feels certain that all malignant tissue was removed at the time of the biopsy, and that no enlarged lymph nodes are detectable, he or she may advocate a “wait-and-see” approach with regular follow-up to monitor any change.

If the biopsy examination confirms the presence of cancer, your lymph nodes may be biopsied to search for cancer cells regardless of whether or not the nodes are enlarged. The standard lymph node biopsy is referred to as a dissection, and involves opening up the area, removing multiple nodes, and checking them for cancer. In recent years, however, doctors have experimented with taking out just one or a few nodes to search for cancer. This “sentinel node biopsy” has fewer side effects than a standard lymph node dissection. It remains to be proven whether long-term survival rates are improved by sentinel node biopsy.

The sentinel node is believed to be the lymph node that is the first “filter” for lymphatic fluid that comes from the tumor. Doctors find this node by injecting either a small amount of a radioactive substance or a blue dye at the site of the melanoma, then monitoring which lymph node or nodes collect the tracer material. The implicated node or nodes are removed, and, if cancer is detected, a standard lymph node dissection is carried out. If not, no further surgery is done.

If there are no signs that the cancer has spread beyond the tumor site, most doctors perform at least a chest x-ray to see if cancer has spread to the lungs. If a doctor is more suspicious of advanced disease, CT, MRI, or nuclear scans of the chest, head, abdomen, and pelvis may also be ordered. Doctors also check the skin thoroughly for any sign of a second primary melanoma lesion.

If the cancer has spread, the doctor, usually either a dermatologist who specializes in skin cancer, or an oncologist, a doctor who specializes in the treatment of cancer, will “stage” it. There are several staging systems; one of the most common assigns the cancer a number, I through IV, based on the size of the tumor and the degree to which it has spread.

• Stage I: The tumor is in the outer layer of the skin (epidermis), and may have reached the upper part of the dermis (the inner layer of skin), but no further. The lesion is less than one sixteenth of an inch thick (a little less than the thickness of a penny).
• Stage II: The tumor has spread to the lower part of the dermis, but not into the surrounding tissue or lymph nodes. The lesion is less than one-sixth of an inch thick (a little less than the thickness of two quarters).
• Stage III: The tumor has any one of the following characteristics: it is more than one-sixth of an inch thick, it has spread to the tissue under the skin, there are other tumors growing within one inch of the origin tumor, or the tumor has spread to nearby lymph nodes.
• Stage IV: The tumor has spread to other organs or lymph nodes distant from the original tumor site.

Prevention and Screening

Protection from excessive sun exposure—especially though frequent use of sunscreen with SPF 15 or higher, protective clothing, and avoiding the midday sun—is essential for reducing the risk of all types of skin cancer. Light-skinned individuals who burn easily should be especially cautious. The following precautions should be taken by everyone to guard against excessive exposure to UVA and UVB radiation:

• Try to schedule time outdoors for sports and other recreational activities before 10am and after 4pm. By doing this you will avoid excessive exposure to UVA and UVB radiation. The amount of UV radiation depends on the angle of the sun, not how hot or bright it appears outside. Clouds and haze do not block harmful radiation.
• When outdoors, wear clothes that cover as much skin as possible; such as lightweight, long-sleeved shirts, long pants, and a broad-brimmed hat.
• Use particular care around reflective surfaces such as water, sand, concrete, and white-painted areas.
• Everyone over 6 months of age should use a broad-based sunscreen that protects from UVA and UVB rays, and has a skin protection factor (SPF) of at least 15. Use SPF 30 or higher if you burn easily, or are at high altitudes where sunlight is more intense. Apply to exposed skin and re-apply every two hours, or after exercising or going in the water. Use a higher SPF factor for more intense conditions, e.g., high altitudes, skiing, or the beach. Sunblocks, products that contain zinc or titanium oxide, and are even more effective than sunscreens, but are less popular because they tend to be pasty and white.
• Parents should shield children under 6 months of age from intense sun exposure, and should protect them with clothing when sun exposure is unavoidable.
• Never go to tanning parlors or use sun lamps. Even though they use mostly UVA rays and do not cause sunburn, they are still believed to be associated with skin cancer. Don't believe advertising claims that they are safe.

Check your skin regularly and have your doctor do so as well at your annual checkup. Experts recommend that individuals conduct a thorough screening of their own skin periodically. Having a partner check your back and other hard-to-see places is ideal. Draw a map of your body and indicate the location of moles, areas of discoloration, and other blemishes. Each month note if a new growth has developed, or if there has been any change in shape, color, or size of lesions. See your doctor if you have any questions or suspicions.

At your annual checkup, ask your provider to look at your skin, especially in areas you can't see. People with major risk factors, such as a history of significant sun exposure, multiple moles, and a fair complexion with a history of burning easily, should be checked at least annually by a dermatologist.