Melanoma

Introduction

Melanoma is the most serious cancer of the skin. In some parts of the world, especially among Western countries, the number of people who develop melanoma is increasing faster than 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.

What Is Melanoma?

Melanoma is a type of skin cancer. It begins in certain 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.

The Skin

The skin is the body's largest organ. It protects against heat, sunlight, injury, and infection. It helps regulate body temperature, stores water and fat, and produces vitamin D. The skin has two main layers: the outer epidermis and the inner dermis.
The epidermis is mostly made up of flat, scalelike cells called squamous cells. Round cells called basal cells lie under the squamous cells in the epidermis. The lower part of the epidermis also contains melanocytes.
The dermis contains blood vessels, lymphatic vessels, hair follicles, and glands. Some of these glands produce sweat, which helps regulate body temperature, and some produce sebum, an oily substance that helps keep the skin from drying out. Sweat and sebum reach the skin's surface through tiny openings called pores.

Melanocytes and Moles

Melanocytes are found throughout the lower part of the epidermis. They 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 benign (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 of these flesh-colored, pink, tan, or brown areas on the skin. 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. Moles generally grow or change only slightly over a long period of time. They tend to fade away in older people. When moles are surgically removed, they normally do not return.

Cancer

Cancer is a group of many different diseases that have some important things in common. They all begin in cells. Normally, cells grow and divide to produce more cells only when the body needs them. This orderly process helps keep the body healthy. Sometimes cells keep dividing when new cells are not needed, creating a mass of extra tissue. This mass is called a growth or tumor. Tumors can be benign or malignant.

• Benign tumors are not cancer. They often can be removed and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body. Most importantly, benign tumors are rarely a threat to life.
• Malignant tumors are cancer. Cells in malignant tumors are abnormal and divide without control or order. These cancer cells can invade and destroy the tissue around them. Cancer cells can also break away from a malignant tumor and enter the bloodstream or lymphatic system (the tissues and organs that produce and store cells that fight infection and disease). This process, called metastasis, is how cancer spreads from the original tumor to form new tumors in other parts of the body. When cancer spreads (metastasizes) to another part of the body, the new tumor has the same kind of abnormal cells and the same name as the original tumor.

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 and is called ocular melanoma or intraocular melanoma. Rarely, melanoma may arise in the meninges, the digestive tract, lymph node, or other areas where melanocytes are found. Melanomas arising in areas other than the skin are not discussed in this booklet.

Melanoma can occur on any skin surface. In men, it is often found on the trunk (the area from the shoulders to the hips) or the head and neck. In women, melanoma 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. The chance of developing melanoma increases with age, but this disease affects people of all age groups. Melanoma is one of the most common cancers in young adults.

When melanoma spreads, cancer cells are also found in the lymph nodes (also called lymph glands). 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 rather than liver, lung, or brain cancer.

Signs and Symptoms of Melanoma

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, black, abnormal, or "ugly-looking" mole.

If you have a question or concern about something on your skin, do not use these 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.
• Diameter--There is a change in size, usually an increase. Melanomas are usually larger than the eraser of a pencil (5 mm or 1/4 inch).

Melanomas can vary greatly in the ways 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.

Early melanomas may be found when a pre-existing mole changes slightly--such as forming a new black area. Other frequent findings are newly formed fine scales or itching in a mole. In more advanced melanoma, the texture of the mole may change. For example, it may become hard or lumpy. Although melanomas may feel different and more advanced tumors may itch, ooze, or bleed, melanomas usually do not cause pain.

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, invading healthy tissue. When a melanoma becomes thick and deep, the disease often spreads to other parts of the body and is difficult to control.

A skin examination is often part of a routine checkup by a doctor, nurse specialist, or nurse practitioner. People also can check their own skin for new growths or other changes. Changes in the skin or a mole should be reported to the doctor or nurse without delay. The person may be referred to a dermatologist, a doctor who specializes in diseases of the skin.

People who have had melanoma have a high risk of developing a new melanoma. Also, those with relatives who have had this disease have an increased risk. Doctors may advise people at risk to check their skin regularly and to have regular skin exams by a doctor or nurse specialist.

Some people have certain abnormal-looking moles, called dysplastic nevi or atypical moles, that may be more likely than normal moles to develop into melanoma. Most people with dysplastic nevi have just a few of these abnormal moles; others have many. They and their doctor should examine these moles regularly to watch for changes. Dysplastic nevi often look very much like melanoma. Doctors with special training in skin diseases are in the best position to decide whether an abnormal-looking mole should be closely watched or should be removed and checked for cancer.

In some families, many members have a large number of dysplastic nevi, and some have had melanoma. Members of these families have a very high risk for melanoma. Doctors often recommend that they have frequent checkups (every 3 to 6 months) so that any problems can be detected early. The doctor may take pictures of a person's skin to help in detecting any changes that occur.

Diagnosis and Staging

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. If the growth is too large to be removed entirely, the doctor removes a sample of the tissue. A biopsy can usually be done in the doctor's office using a local anesthetics. A pathologist then examines the tissue under a microscope to check for cancer cells. Sometimes it is helpful for more than one pathologist to look at the tissue to determine whether melanoma is present.

A person who needs a biopsy may want to ask the doctor some of the following questions:

• Why do I need to have a biopsy?
• How long will it take? Will it hurt?
• Will the entire tumor be removed?
• What side effects can I expect?
• How soon will I know the results?
• If I do have cancer, who will talk with me about treatment? When?

If melanoma is found, the doctor needs to learn the extent, or stage, of the disease before planning treatment. The treatment plan takes into account the location and thickness of the tumor, how deeply the melanoma has invaded the skin, and whether melanoma cells have spread to nearby lymph nodes or other parts of the body. Removal of nearby lymph nodes for examination under a microscope is sometimes necessary. (Such surgery may be considered part of the treatment because removing cancerous lymph nodes may help control the disease.) The doctor also does a careful physical exam and, depending on the thickness of the tumor, may order chest x-rays; blood tests; and scans of the liver, bones, and brain.

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