What Is Melanoma?

Melanoma is a type of skin cancer. It begins in cells in the skin called melanocytes. To understand melanoma, it is helpful to know about the skin and about melanocytes—what they do, how they grow, and what happens when they become cancerous.

Melanocytes and Moles

Melanocytes produce melanin, the pigment that gives skin its natural color. When skin is exposed to the sun, melanocytes produce more pigment, causing the skin to tan, or darken.

Sometimes, clusters of melanocytes and surrounding tissue form noncancerous growths called moles. (Doctors also call a mole a nevus; the plural is nevi.) Moles are very common. Most people have between 10 and 40 moles.

Moles may be pink, tan, brown, or a color that is very close to the person’s normal skin tone. People who have dark skin tend to have dark moles. Moles can be flat or raised. They are usually round or oval and smaller than a pencil eraser.

They may be present at birth or may appear later on—usually before age 40. They tend to fade away in older people. When moles are surgically removed, they normally do not return.

 

Melanoma

Melanoma occurs when melanocytes (pigment cells) become malignant. Most pigment cells are in the skin; when melanoma starts in the skin, the disease is called cutaneous melanoma. Melanoma may also occur in the eye (ocular melanoma or intraocular melanoma).


Rarely, melanoma may arise in the meninges, the digestive tract, lymph nodes, or other areas where melanocytes are found. Melanomas that begin in areas other than the skin are not discussed in this booklet.
 
Melanoma is one of the most common cancers. The chance of developing it increases with age, but this disease affects people of all ages. It can occur on any skin surface. In men, melanoma is often found on the trunk (the area between the shoulders and the hips) or the head and neck.

In women, it often develops on the lower legs. Melanoma is rare in black people and others with dark skin. When it does develop in dark-skinned people, it tends to occur under the fingernails or toenails, or on the palms or soles.

When melanoma spreads, cancer cells may show up in nearby lymph nodes. Groups of lymph nodes are found throughout the body. Lymph nodes trap bacteria, cancer cells, or other harmful substances that may be in the lymphatic system.

If the cancer has reached the lymph nodes, it may mean that cancer cells have spread to other parts of the body such as the liver, lungs, or brain. In such cases, the cancer cells in the new tumor are still melanoma cells, and the disease is called metastatic melanoma, not liver, lung, or brain cancer.

 

Melanoma: Who’s at Risk?

No one knows the exact causes of melanoma. Doctors can seldom explain why one person gets melanoma and another does not.

However, research has shown that people with certain risk factors are more likely than others to develop melanoma. A risk factor is anything that increases a person’s chance of developing a disease. Still, many who do get this disease have no known risk factors.

Studies have found the following risk factors for melanoma:

• Dysplastic nevi: Dysplastic nevi are more likely than ordinary moles to become cancerous. Dysplastic nevi are common, and many people have a few of these abnormal moles. The risk of melanoma is greatest for people who have a large number of dysplastic nevi. The risk is especially high for people with a family history of both dysplastic nevi and melanoma.
• Many (more than 50) ordinary moles: Having many moles increases the risk of developing melanoma.
• Fair skin: Melanoma occurs more frequently in people who have fair skin that burns or freckles easily (these people also usually have red or blond hair and blue eyes) than in people with dark skin. White people get melanoma far more often than do black people, probably because light skin is more easily damaged by the sun.
• Personal history of melanoma or skin cancer: People who have been treated for melanoma have a high risk of a second melanoma. Some people develop more than two melanomas. People who had one or more of the common skin cancers (basal cell carcinoma or squamous cell carcinoma) are at increased risk of melanoma.
• Family history of melanoma: Melanoma sometimes runs in families. Having two or more close relatives who have had this disease is a risk factor. About 10 percent of all patients with melanoma have a family member with this disease. When melanoma runs in a family, all family members should be checked regularly by a doctor.
• Weakened immune system: People whose immune system is weakened by certain cancers, by drugs given following organ transplantation, or by HIV are at increased risk of developing melanoma.
• Severe, blistering sunburns: People who have had at least one severe, blistering sunburn as a child or teenager are at increased risk of melanoma. Because of this, doctors advise that parents protect children’s skin from the sun. Such protection may reduce the risk of melanoma later in life. Sunburns in adulthood are also a risk factor for melanoma.

• Ultraviolet (UV) radiation: Experts believe that much of the worldwide increase in melanoma is related to an increase in the amount of time people spend in the sun. This disease is also more common in people who live in areas that get large amounts of UV radiation from the sun.

UV radiation from the sun causes premature aging of the skin and skin damage that can lead to melanoma. Artificial sources of UV radiation, such as sunlamps and tanning booths, also can cause skin damage and increase the risk of melanoma. Doctors encourage people to limit their exposure to natural UV radiation and to avoid artificial sources.

People who are concerned about developing melanoma should talk with their doctor about the disease, the symptoms to watch for, and an appropriate schedule for checkups. The doctor’s advice will be based on the person’s personal and family history, medical history, and other risk factors.

 

Signs and Symptoms

Often, the first sign of melanoma is a change in the size, shape, color, or feel of an existing mole. Most melanomas have a black or blue-black area. Melanoma also may appear as a new mole. It may be black, abnormal, or “ugly looking.”

If you have a question or concern about something on your skin, see your doctor. Do not use the following pictures to try to diagnose it yourself. Pictures are useful examples, but they cannot take the place of a doctor’s examination.

Thinking of “ABCD” can help you remember what to watch for:

• Asymmetry—The shape of one half does not match the other.
• Border—The edges are often ragged, notched, blurred, or irregular in outline; the pigment may spread into the surrounding skin.
• Color—The color is uneven. Shades of black, brown, and tan may be present. Areas of white, grey, red, pink, or blue also may be seen.

Melanomas can vary greatly in how they look. Many show all of the ABCD features. However, some may show changes or abnormalities in only one or two of the ABCD features.

Melanomas in an early stage may be found when an existing mole changes slightly, for example, when a new black area forms. Newly formed fine scales and itching in a mole also are common symptoms of early melanoma.

In more advanced melanoma, the texture of the mole may change. For example, it may become hard or lumpy. Melanomas may feel different from regular moles. More advanced tumors may itch, ooze, or bleed. But melanomas usually do not cause pain.

A skin examination is often part of a routine checkup by a health care provider. People also can check their own skin for new growths or other changes. (The “How To Do a Skin Self-Exam” section has a simple guide on how to do this skin self-exam.) Changes in the skin, such as a change in a mole, should be reported to the health care provider right away.

The person may be referred to a dermatologist, a doctor who specializes in diseases of the skin.

Melanoma can be cured if it is diagnosed and treated when the tumor is thin and has not deeply invaded the skin. However, if a melanoma is not removed at its early stages, cancer cells may grow downward from the skin surface and invade healthy tissue. When a melanoma becomes thick and deep, the disease often spreads to other parts of the body and is difficult to control.

People who have had melanoma have a high risk of developing a new melanoma. People at risk for any reason should check their skin regularly and have regular skin exams by a health care provider.

Diagnosis

If the doctor suspects that a spot on the skin is melanoma, the patient will need to have a biopsy. A biopsy is the only way to make a definite diagnosis. In this procedure, the doctor tries to remove all of the suspicious-looking growth.

This is an excisional biopsy. If the growth is too large to be removed entirely, the doctor removes a sample of the tissue. The doctor will never "shave off" or cauterize a growth that might be melanoma.

A biopsy can usually be done in the doctor’s office using local anesthesia. A pathologist then examines the tissue under a microscope to check for cancer cells. Sometimes it is helpful for more than one pathologist to check the tissue for cancer cells.

Treatment

The doctor can describe treatment choices and discuss the results expected with each treatment option. The doctor and patient can work together to develop a treatment plan that fits the patient’s needs.

Treatment for melanoma depends on the extent of the disease, the patient’s age and general health, and other factors.

People with melanoma are often treated by a team of specialists. The team may include a dermatologist, surgeon, medical oncologist, radiation oncologist, and plastic surgeon.

Diameter—There is a change in size, usually an increase. Melanomas are usually larger than the eraser of a pencil (1/4 inch or 5 millimeters).


Source:www.nih.gov
Last Editorial Review: 25/1/2010