Understanding Melanoma

The skin is the largest organ in the body. It covers and protects the inside of the body, provides a barrier against germs and prevents the loss of too much water and other fluids. Cancers of the skin are divided into two main categories: nonmelanoma and melanoma. This section was put together to help you learn more about melanoma skin cancer.

WHAT IS MELANOMA?

Although melanoma is the least common type of skin cancer, it is the most serious form of the disease. It occurs in certain cells in the skin called melanocytes, which are found in the outermost layers of the skin (the epidermis). Melanocytes produce the protective pigment called melanin that gives skin its natural color. Melanoma begins when melanocytes become malignant, which means they are abnormal and grow uncontrollably. Cells can become malignant through random changes or mutations that can occur in a cell’s genetic code.

WHAT IS METASTATIC MELANOMA?

Melanoma is described as metastatic when the cancer has metastasized, which means that it has spread from the original area of the disease to distant sites such as the liver, lungs or brain.

HOW MANY PEOPLE GET MELANOMA?

In some parts of the world, especially among Western countries, the number of people who develop melanoma is increasing faster than for any other cancer. In the United States, for example, the number of new cases of melanoma has more than doubled in the past 20 years. The American Cancer Society estimates that in 2004, there will be 55,100 new cases of melanoma in the United States, and about 7,910 people will die of the disease. Although melanoma only accounts for about 4 percent of skin cancer cases, it causes approximately 79 percent of skin cancer deaths.

WHAT CAUSES MELANOMA?

Exactly what causes melanoma skin cancer remains unknown but certain risk factors are known to be linked with the disease. Risk factors for melanoma include:

• Many moles or some large moles
• Fair skin, freckling and light hair
• Family history
• Immune suppression (such as from certain illnesses or immunosuppressive medications)
• UV radiation such as sunlight and tanning lamps
• Age over 50, although younger people can also get melanoma
• Xeroderma pigmentosum (XP), a rare genetic condition. People with XP are less able to repair damage caused by sunlight and are therefore at greater risk of melanoma.

CAN MELANOMA BE PREVENTED?

The best way to lower the risk of melanoma is to avoid too much exposure to the sun and other sources of UV light. The American Cancer Society has recommended the following to help prevent skin cancer:

• Avoid being outdoor in sunlight too long, especially in the middle of the day when ultraviolet light is most intense.
• Protect skin with clothing, including a shirt and a hat with a broad brim.
• Use sunscreen with an SPF of 15 or more. Use a palmful for the whole body and reapply every two hours. Use sunscreen even on hazy days or days with light or broken cloud cover, and do not stay out in the sun longer because you are using sunscreen.
• Wear sunglasses. Wrap-around sunglasses with 99 percent to 100 percent UV absorption provide the best protection.
• Avoid other sources of UV light such as tanning beds and sun lamps.
• Be especially careful about sun protection for children. People who suffer severe blistering sunburns, particularly in childhood or teenage years, are at increased risk of melanoma.
• Have a doctor check suspicious moles and have them removed, if indicated.

HOW IS MELANOMA DIAGNOSED?

If skin cancer is suspected, the physician will conduct additional medical examinations and tests to determine if it is skin cancer (melanoma or nonmelanoma) or some other skin condition.

The doctor will usually obtain a patient’s medical history first, asking questions about symptoms and various risk factors, such as family history and past exposures to known causes of skin cancer.

During the physical examination, the size, shape, color and texture of the area in question will be examined, and the doctor will check for bleeding or scaling. Although melanomas can vary greatly in the ways they look, the ABCDE test can be helpful in identifying suspicious moles:

• Asymmetry: the shape of one half of the mole does not match the other
• Border: the edges of the mole are often ragged, notched, blurred or irregular in outline, and the pigment may spread into the surrounding skin
• Color: the color is uneven, possibly with shades of black, brown and tan, and sometimes areas of white, gray, red, pink or blue
• Diameter: there is a change (usually an increase) in size
• Elevation: the mole is raised or elevated above the skin

During the examination, the rest of the body will also be checked for spots and moles that may be related to skin cancer. The doctor may also examine lymph nodes in the groin, underarm, or neck areas near the abnormal area of skin.

If melanoma is suspected, a skin biopsy is conducted, which means that the doctor will take a sample of skin from the suspicious area for examination under a microscope. There are different methods of conducting skin biopsies, including shave biopsy, punch biopsy, and excisional or incisional biopsies. Because these different methods produce different types of scars, the possibility of scarring should be discussed with the doctor before the biopsies are performed. All skin biopsies are performed using a local anesthetic. Patients usually feel a small needle stick and a little burning with some pressure, but no pain.

Metastatic Melanoma

Although many melanomas are completely cured, some melanomas spread so quickly that a patient can have large masses of melanoma in the lymph nodes, lungs, brain, gastrointestinal tract or liver while the original skin melanoma is still small. Melanoma that has spread to other parts of the body may not be detectable until long after the original melanoma was removed from the skin.

When such spread has occurred, the metastatic melanoma in certain organs might be confused with a cancer starting in that organ. For example, melanoma that has spread to the lung might be confused with a primary lung cancer (cancer that starts in the lung). There are special tests that can be done on biopsy samples that can tell whether it is a melanoma or some other kind of cancer. This is important because different cancers are often given different treatments.

WHAT IS CANCER STAGING?

Staging is the process of finding out how far the cancer has spread (or metastasized). This includes describing the size of the cancer as well as the extent to which the cancer has spread to other organs. Staging is very important because, to a large extent, treatment and outlook for recovery depend on the stage of cancer.

Stage	Description
Stage 0	The melanoma has not spread and is still limited to the skin’s epidermis.
Stage I	The cancer has spread to the dermis layer of skin but has not reached the lymph nodes. Stage I tumors are less than 1.5 mm thick.
Stage II	The melanoma has spread to the dermis, but has not reached the lymph nodes. Stage II tumors are more than 1.5 mm thick.
Stage III	The cancer has spread to lymph nodes near the affected skin area but not to distant areas of the body.
Stage IV	The melanoma has spread to organs such as the lung, liver or brain, or to distant lymph nodes or areas of the skin.

Source: American Joint Committee on Cancer