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Melanoma
Statistics
Melanoma is currently the sixth most
common cancer in American men and the
seventh most common in American women.
The median age at diagnosis is between
45 and 55, although 25% of cases occur
in individuals before age 40. It is
the second most common cancer in women
between the ages of 20 and 35, and the
leading cause of cancer death in women
ages 25 to 30.
Melanoma is the least common but the
most deadly skin cancer, accounting
for only about 4% of all cases but 79%
of skin cancer deaths. This year, the
American Cancer Society estimates there
will be 53,600 new cases of melanoma
in the United States and 7,400 deaths
from the disease.
The United States has experienced a
dramatic increase in the number of melanoma
cases over the past few decades. According
to the American Cancer Society, the
incidence rate for melanoma (number
of new cases of melanoma per 100,000
people each year) has more than doubled
since 1973.
Causes
of Melanoma
Ultraviolet (UV) radiation from the
sun is the most recognized cause of
all types of skin cancer, including
melanoma. Tanning lamps are another
source of UV radiation. The invisible
effects of UV radiation accumulate over
a lifetime. This year's and next year's
tans add to the effects. The effects
include aging of the skin or, worse,
cancer.
To a degree, the body can protect itself
against UV rays. The means of protection
is melanin, a dark pigment that screens
out some UV radiation. (Melanin is also
the pigment responsible for skin, eye,
and hair color.) Exposure of the skin
to the sun results in increased production
of melanin by cells known as melanocytes.
A tan is the result of melanin production.
Although dark-skinned people (who have
more melanin than light-skinned people)
have lower skin cancer rates than the
fair skinned, anyone can develop skin
cancer.
Melanoma:
Risk Factors
A person may have an increased risk
of melanoma if he or she:
- Is an adult. The risk of
melanoma increases with age.
The risk of developing melanoma
is 88 times greater after
age 15. Melanoma among children
is extremely rare.
- Has a changed or persistently
changing mole. Melanoma often
develops in an existing mole
of any size that changes in
color, shape, thickness, area,
or sensation. Bleeding, pain,
and ulceration usually are
late signs that a mole has
become melanoma. One percent
of melanomas lack pigmentation
and may appear as pink or
red nodules. Not all changes
in a mole, however, indicate
melanoma.
- Has one or more large or
irregularly pigmented skin
growths. This category includes:
- prominent moles --
those the size of pencil
erasers (about 4 millimeters
in diameter) or larger
- dysplastic moles --
large, unevenly colored
moles that have fuzzy
or irregular borders and
a flat component
- lentigo malignas --
precancerous brown "shoe
polish stains" on
sun-damaged skin; these
are particularly prevalent
in the elderly
- other atypical pigmented
skin growths
- Congenital moles. Congenital
moles are moles that are
present at birth. Small
congenital moles occur
in 1 percent of newborns.
Infants born with a small
congenital mole have an
estimated 5 percent risk
of developing melanoma
by age 60. Giant congenital
moles are more infrequent
-- only one in 500,000
newborns has one. The
lifetime melanoma risk
for a person with a giant
congenital mole is approximately
10 percent.
- Is light skinned. The incidence
of melanoma among whites in
the United States is approximately
12 times greater than that
among nonwhites. Among nonwhites,
melanoma often appears on
the palms of the hands, soles
of the feet, and mucous membranes;
in nail beds; and at the site
of a congenital, atypical,
or changing pigmented skin
growth.
- Is sensitive to the sun.
The tendency to burn easily
and tan poorly -- regardless
of skin color -- is associated
with a threefold increase
in the risk of melanoma.
- Has experienced excessive
sun exposure. Excessive sun
exposure, particularly during
childhood, is associated with
a threefold increase in melanoma
risk. The relationship between
sun exposure and melanoma
is not as clear as it is for
nonmelanoma skin cancer. Sun
sensitivity and excessive
sun exposure may be responsible
for bringing out the trait
that causes atypical moles
in genetically predisposed
people, or sun exposure may
cause potentially precancerous
moles to become cancerous.
Excessive sun exposure often
occurs during recreational
activities.
- Has a history of melanoma.
People who have had one melanoma
have a ninefold increase in
the risk of developing a second
primary melanoma. A past melanoma
patient should have a thorough
skin exam at least yearly,
either from a doctor or from
someone familiar with skin-screening
procedures.
- Has parents, brothers,
sisters, or children with
a history of melanoma. The
risk of melanoma increases
eightfold if a person has
a relative in the immediate
family who has had melanoma.
Blood relatives of people
who have had melanoma should
be examined regularly for
atypical moles and early-stage
melanoma.
- Has a suppressed immune
system. A person whose immune
system is compromised as a
result of disease or immunosuppressive
therapy (such as the therapy
that helps prevent organ rejection
after transplantation surgery)
has a fourfold increase in
melanoma risk.
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Diagnosis
and Evaluation of Melanoma
Fortunately, when melanoma is detected
early, it is highly curable. Self-screening
and regular examination by a doctor
are the keys to early diagnosis.
If screening discovers a growth that
might be melanoma, the growth must be
evaluated by an expert. A doctor removes
a small sample of the tissue and a pathologist
examines the tissue under a microscope.
The pathologist assesses the tumor's
characteristics -- such as tumor thickness
-- that influence prognosis and treatment.
Tumors less than 3/100 inch (0.76 millimeter)
thick are an increasing fraction of
new cases; patients with tumors of this
size who receive prompt, appropriate
treatment have a 98 percent chance of
five-year survival. Patients with tumors
larger than 1/6 inch (4 millimeters)
thick have a 50 percent chance of five-year
survival. Large tumors are becoming
less common as the public becomes more
aware of the early signs of melanoma
and is more likely to seek treatment
promptly. If the cancer has spread to
the lymph nodes, as it has in 15 percent
of new patients, the chance for five-year
survival drops to 25 to 40 percent.
Source: American
Cancer Society, 2002. (www.cancer.org)
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