Cancer develops when DNA,
the molecule found in cells that encodes genetic information,
becomes damaged and the body cannot repair the damage. These damaged
cells begin to grow and divide uncontrollably. When this occurs in
the skin, skin cancer develops. As the damaged cells multiply, they
form a tumor. Since skin cancer generally develops in the epidermis,
the outermost layers of skin, a tumor is usually clearly visible.
This makes most skin cancers detectable in the early stages.
Types of Skin Cancer
Three types of skin cancer account for nearly 100% of all diagnosed
cases. Each of these three cancers begins in a different type of
cell within the skin, and each cancer is named for the type of cell
in which it begins. Skin cancers are divided into one of two classes
- nonmelanoma skin cancers and melanoma. Melanoma is the deadliest
form of skin cancer.
The different types of skin cancer are:
Basal cell carcinoma (BCC): The most common cancer in humans,
BCC develops in more than 1 million people every year in the United
States alone. About 80% of all skin cancers are BCC, a cancer that
develops in the basal cells - skin cells located in the lowest layer
of the epidermis. BCC can take several forms. It can appear as a
shiny translucent or pearly nodule, a sore that continuously heals
and then re-opens, a pink slightly elevated growth, reddish
irritated patches of skin, or a waxy scar. Most BCCs appear on skin
with a history of exposure to the sun, such as the face, ears,
scalp, and upper trunk. These tumors tend to grow slowly and can
take years to reach Ĺ inch in size. While these tumors very rarely
metastasize (cancer spreads to other parts of the body),
dermatologists encourage early diagnosis and treatment to prevent
extensive damage to surrounding tissue.
Squamous cell carcinoma (SCC): About 16% of diagnosed skin
cancers are SCC. This cancer begins in the squamous cells, which are
found in the upper layer of the epidermis. About 200,000 cases are
diagnosed ever year. SCC tends to develop in fair-skinned
middle-aged and elderly people who have had long-term sun exposure.
It most often appears as a crusted or scaly area of skin with a red
inflamed base that resembles a growing tumor, non-healing ulcer, or
crusted-over patch of skin. While most commonly found on sun-exposed
areas of the body, it can develop anywhere, including the inside of
the mouth and the genitalia. SCC may arise from actinic keratoses,
which are dry, scaly lesions that may be skin-colored, reddish-brown
or yellowish-black. SCC requires early treatment to prevent
Melanoma: Accounting for about 4% of all diagnosed skin
cancers, melanoma begins in the melanocytes, cells within the
epidermis that give skin its color. Melanoma has been coined ďthe
most lethal form of skin cancerĒ because it can rapidly spread to
the lymph system and internal organs. In the United States alone,
approximately one person dies from melanoma every hour. Older
Caucasian men have the highest mortality rate. Dermatologists
believe this is due to the fact that they are less likely to heed
the early warning signs. With early detection and proper treatment,
the cure rate for melanoma is about 95%. Once its spreads, the
prognosis is poor. Melanoma most often develops in a pre-existing
mole or looks like a new mole, which is why it is important for
people to know what their moles look like and be able to detect
changes to existing moles and spot new moles.
Other nonmelanoma skin cancers: All other skin cancers
combined account for less than 1% of diagnosed cases. These are
classified as nonmelanoma skin cancers and include Merkel cell
carcinoma, dermatofibromasarcoma protuberans, Pagetís disease and
cutaneous T-cell lymphoma.
Sun exposure is the leading cause of skin cancer. According to the
American Cancer Society, ďMany of the more than 1 million skin
cancers diagnosed each year could be prevented with protection from
the sunís rays.Ē Scientists now know that exposure to the sunís
ultraviolet (UV) rays damages DNA in the skin. The body can usually
repair this damage before gene mutations occur and cancer develops.
When a personís body cannot repair the damaged DNA, which can occur
with cumulative sun exposure, cancer develops.
In some cases, skin cancer is an inherited condition. Between 5% and
10% of melanomas develop in people with a family history of
Who Gets Skin Cancer?
Skin cancer develops in people of all colors, from the palest to the
darkest. However, skin cancer is most likely to occur in those who
have fair skin, light-colored eyes, blonde or red hair, a tendency
to burn or freckle when exposed to the sun, and a history of sun
exposure. Anyone with a family history of skin cancer also has an
increased risk of developing skin cancer. In dark-skinned
individuals, melanoma most often develops on non-sun-exposed areas,
such as the foot, underneath nails, and on the mucous membranes of
the mouth, nasal passages, or genitals. Those with fair skin also
can have melanoma develop in these areas.
Skin Cancer Rates Rising
While Americans now recognize that overexposure to the sun is
unhealthy, the fact remains that most do not protect their skin from
the sunís harmful rays. As a result, skin cancer is common
in the United States. More than 1 million nonmelanoma skin cancers are diagnosed
each year, and approximately one person dies from melanoma every
If current trends continue, 1 in 5 Americans will develop skin
cancer during their lifetime. Melanoma continues to rise at an
alarming rate. In 1930, 1 in 5,000 Americans was likely to develop
melanoma during their lifetime. By 2004, this ratio jumped to 1 in
65. Today, melanoma is the second most common cancer in women
aged 20 to 29.
Prevention and Early Detection Key
Sun protection can significantly decrease a personís risk of
developing skin cancer. Sun protection practices include staying out
of the sun between 10 a.m. and 4 p.m. when the rays are strongest,
applying a broad-spectrum (offers UVA and UVB protection) sunscreen
with a Sun Protection Factor (SPF) of 30 or higher year-round to all
exposed skin, and wearing a protective clothing, such as a
wide-brimmed hat and sunglasses when outdoors.
Since skin cancer is so prevalent today, dermatologists also
recommend that everyone learn how to recognize the signs of skin
cancer, use this knowledge to perform regular examinations of their
skin, and see a dermatologist annually (more frequently if at high
risk) for an exam. Skin cancer is highly curable with early
detection and proper treatment.
content solely developed by the American Academy of Dermatology
1 in 5 Americans
will develop some form of skin cancer during their
American Academy of Dermatology
This basal cell carcinoma
appears as a shiny, almost translucent nodule on the
carcinoma developed on the scalp of this fair-skinned
This melanoma has the "ABCD"
warning signs of melanoma:
irregularity, Color varies, and Diameter
larger than a pencil eraser - melanoma can be smaller.
If you notice a mole that differs from others, or one
that changes, bleeds, or itches,
see a dermatologist.
used with permission of the American Academy of
Dermatology National Library of Dermatologic Teaching
and text that provide
step-by-step instructions for performing a
self-examination of your skin.