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Additional Information
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Melanoma
is the most serious type of cancer of the skin. Each year
in the United States, more than 53,600 people learn they
have melanoma.
In some parts of the world, especially among Western countries,
melanoma is becoming more common every year. In the United
States, for example, the percentage of people who develop
melanoma has more than doubled in the past 30 years.
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.
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.
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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.
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The dermis contains blood vessels, lymph
vessels, hair follicles,
and glands.
Some of these glands produce sweat, which helps regulate
body temperature. Other glands 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 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.
Understanding Cancer
Cancer begins in cells, the building blocks that make up
tissues. Tissues make up the organs of the body. Normally,
cells grow and divide to form new cells as the body needs
them. When cells grow old, they die, and new cells take their
place.
Sometimes this orderly process goes wrong. New cells form
when the body does not need them, and old cells do not die
when they should. These extra cells can form a mass of tissue
called a growth or tumor.
Not all tumors are cancer.
Tumors can be benign or malignant:
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. The Cancer Information Service
(1-800-4-CANCER) can provide information about these types
of melanoma.
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:
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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.
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Many (more than 50) ordinary moles:
Having many moles increases the risk of developing melanoma.
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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.
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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.
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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.
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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.
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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.
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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. In the United States, for
example, melanoma is more common in Texas than in Minnesota,
where the sun is not as strong. 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.
Doctors recommend that people take steps to help prevent
and reduce the risk of melanoma caused by UV radiation:
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Avoid exposure to the midday sun (from 10 a.m. to 4
p.m.) whenever possible. When your shadow is shorter
than you are, remember to protect yourself from the sun.
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If you must be outside, wear long sleeves, long pants,
and a hat with a wide brim.
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Protect yourself from UV radiation that can penetrate
light clothing, windshields, and windows.
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Protect yourself from UV radiation reflected by sand,
water, snow, and ice.
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Help protect your skin by using a lotion, cream, or
gel that contains sunscreen.
Many doctors believe sunscreens may help prevent melanoma,
especially sunscreens that reflect, absorb, and/or scatter
both types of ultraviolet radiation. These sunscreen
products will be labeled with “broad-spectrum coverage.” Sunscreens
are rated in strength according to a sun protection factor
(SPF). The higher the SPF, the more sunburn protection
is provided. Sunscreens with an SPF value of 2 to 11
provide minimal protection against sunburns. Sunscreens
with an SPF of 12 to 29 provide moderate protection.
Those with an SPF of 30 or higher provide the most protection
against sunburn.
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Wear sunglasses that have UV-absorbing lenses. The label
should specify that the lenses block at least 99 percent
of UVA and UVB
radiation. Sunglasses can protect both the eyes
and the skin around the eyes.
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.
To read the rest of this great article from the National
Cancer Institute, please click here: http://www.nci.nih.gov/cancertopics/wyntk/melanoma/page7
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