SKIN CANCER

Causes

Skin cancer is the most common type of cancer in the United States. According to current estimates, 40 to 50 percent of Americans who live to age 65 will have skin cancer at least once. Melanoma is the most serious of the skin cancers, and the number of people who develop melanoma is increasing at a faster rate than that of any other cancer.

Although anyone can get skin cancer, the risk is greatest for people who have fair skin that freckles easily, and often those with red or blond hair and blue or light-colored eyes.

Ultraviolet (UV) Radiation from the sun is the main cause of skin cancer. Artificial sources of UV radiation, such as sunlamps and tanning booths, can also cause skin cancer. The risk of developing skin cancer is affected by where a person lives.

People who live in areas that get high levels of UV radiation from the sun are more likely to get skin cancer. In the United States, for example, skin cancer is more common in Texas than it is in Minnesota, where the sun is not as strong.

Worldwide, the highest rates of skin cancer are found in areas that receive high amounts of UV radiation such as South Africa, Australia and New Zealand.

The risk of developing skin cancer is related to lifetime exposure to UV radiation. Most skin cancers appear after age 50, but the sun's damaging effects begin at an early age. Therefore, protection should start in childhood to prevent skin cancer later in life.

Ultraviolet (UV) light exposure, most commonly from sunlight, is overwhelmingly the most frequent cause of skin cancer.

Other important causes of skin cancer include the following:

Use of tanning booths

Exposure to unusually high levels of x-rays

Contact with certain chemicals-arsenic (miners, sheep shearers, and farmers), hydrocarbons in tar, oils, and soot (may cause squamous cell carcinoma)

The following people are at the greatest risk:

  • People with fair skin, especially types that freckle, sunburn easily, or become painful in the sun
  • People with light (blond or red) hair and blue or green eyes
  • Those with certain genetic disorders such as albinism,
  • People who have already been treated for skin cancer
  • People with numerous moles, unusual moles, or large moles that were present at birth
  • People with close family members who have developed skin cancer
  • People who had at least one severe sunburn early in life

Ultraviolet (UV) radiation from the sun is the number-one cause of skin cancer, but UV light from tanning beds is just as harmful. Exposure to sunlight during the winter months puts you at the same risk as exposure during the summertime.

Cumulative sun exposure causes mainly basal cell and squamous cell skin cancer, while episodes of severe sunburns, usually before age 18, can cause melanoma later in life. Other less common causes are repeated X-ray exposure and occupational exposure to certain chemicals
.

Although anyone can get skin cancer, the risk is greatest for people who have fair or freckled skin that burns easily, light eyes and blond or red hair. Darker skinned individuals are also susceptible to all types of skin cancer, although their risk is substantially lower.

Aside from complexion, other risk factors include having a family history or personal history of skin cancer, having an outdoor job and living in a sunny climate. A history of severe sunburns and an abundance of large and irregularly-shaped moles are risk factors unique to melanoma.

Damage

Chronic exposure to the sun also causes premature aging, which over time can make the skin become thick, wrinkled, and leathery.

Cataracts are a form of eye damage in which a loss of transparency in the lens of the eye clouds vision. If left untreated, cataracts can lead to blindness. Research has shown that UV radiation increases the likelihood of certain cataracts. Although curable with modern eye surgery, cataracts diminish the eyesight of millions of Americans and cost billions of dollars in medical care each year.

Other kinds of eye damage include pterygium (tissue growth that can block vision), skin cancer around the eyes, and degeneration of the macula (the part of the retina where visual perception is most acute). All of these problems can be lessened with proper eye protection. Look for sunglasses, glasses or contact lenses if you wear them, that offer 99 to 100 percent UV protection.

The sun's rays make us feel good, and in the short term, make us look good. But our love affair isn't a two-way street: Exposure to sun causes most of the wrinkles and age spots on our faces. Consider this: One woman at age 40 who has protected her skin from the sun actually has the skin of a 30-year-old!

Sun exposure causes most of the skin changes that we think of as a normal part of aging. Over time, the sun's ultraviolet (UV) light damages the fibers in the skin called elastin. When these fibers break down, the skin begins to sag, stretch, and lose its ability to go back into place after stretching. The skin also bruises and tears more easily -- taking longer to heal. So while sun damage to the skin may not be apparent when you're young, it will definitely show later in life.

Exposure to the sun causes:

• Pre-cancerous (actinic keratosis) and cancerous (basal cell carcinoma, squamous cell carcinoma and melanoma) skin lesions - caused by loss of the skin's immune function

• Benign tumors

• Fine and coarse wrinkles

• Freckles

• Discolored areas of the skin, called mottled pigmentation

• Sallowness -- a yellow discoloration of the skin

• Telangiectasias -- the dilation of small blood vessels under the skin

• Elastosis -- the destruction of the elastic and collagen tissue (causing lines and wrinkles)

Immune Suppression

Scientists have found that overexposure to UV radiation may suppress proper functioning of the body’s immune system and the skin’s natural defenses. For example, the skin normally mounts a defense against foreign invaders such as cancers and infections. But overexposure to UV radiation can weaken the immune system, reducing the skin’s ability to protect against these invaders.

The most common types of sun damage to the skin are:

·  Dry skin — Sun-exposed skin can gradually lose moisture and essential oils, making it appear dry, flaky and prematurely wrinkled, even in younger people.

·  Sunburn — Sunburn is the common name for the skin injury that appears immediately after the skin is exposed to UV radiation. Mild sunburn causes only painful reddening of the skin, but more severe cases can produce tiny fluid-filled bumps (vesicles) or larger blisters.

·  Actinic keratosis — This is a tiny bump that feels like sandpaper or a small, scaly patch of sun-damaged skin that has a pink, red, yellow or brownish tint. Unlike suntan markings or sunburns, an actinic keratosis does not usually go away unless it is frozen, chemically treated or removed by a doctor. An actinic keratosis develops in areas of skin that have undergone repeated or long-term exposure to the sun's UV light, and it is a warning sign of increased risk of skin cancer. About 10% to 15% of actinic keratoses eventually change into squamous cell cancers of the skin.

·  Long-term changes in the skin's collagen (a structural protein) — These changes include photoaging (premature aging of the skin because of sun exposure) and actinic purpura (bleeding from fragile blood vessels beneath the skin surface). In photoaging, the skin develops wrinkles and fine lines because of changes in the collagen of a deep layer of the skin called the dermis. In actinic purpura, UV radiation damages the structural collagen that supports the walls of the skin's tiny blood vessels. Particularly in older people, this collagen damage makes blood vessels more fragile and more likely to rupture following a slight impact.

Description/types

Skin cancer is the most prevalent form of all cancers in the U.S. and the number of cases continues to rise. It is the uncontrolled growth of abnormal skin cells. This rapid growth results in tumors, which are either benign (noncancerous) or malignant (cancerous).

The most common kinds of skin cancer are basal cell carcinoma and squamous cell carcinoma (also called nonmelanoma skin cancer). Carcinoma is cancer that begins in the cells that cover or line an organ. Melanoma is a malignancy of the melanocytes and is the most serious form of skin cancer.

Basal cell carcinoma is a slow-growing cancer that seldom spreads to other parts of the body.

Squamous cell carcinoma also rarely spreads, but it does so more often than basal cell carcinoma. It is important that skin cancers be found and treated early because they can invade and destroy nearby tissue.

Melanoma occurs when melanocytes become malignant. When melanoma starts in the skin (it may also start in other parts of the body such as the eye) the disease is called cutaneous melanoma. When melanoma spreads (metastasizes), cancer cells are also found in the lymph nodes, and it may mean that the cancer has also spread to other parts of the body such as the liver, lungs or brain. The cancer cells of the new tumor are still melanoma cells, and the disease is called metastatic melanoma rather than liver, lung or brain cancer.

There are three main types of skin cancer: basal cell carcinoma, squamous cell carcinoma and melanoma.
Basal cell and squamous cell cancers are less serious types and make up 95% of all skin cancers. Also referred to as non-melanoma skin cancers, they are highly curable when treated early. Melanoma, made up of abnormal skin pigment cells called melanocytes, is the most serious form of skin cancer and causes 75% of all skin cancer deaths. Left untreated, it can spread to other organs and is difficult to control.

• Basal cell carcinoma may appear as a small, smooth, pearly or waxy bump on the face ears and neck, or as a flat pink, red or brown lesion on the trunk or arms and legs.

• Squamous cell carcinoma can appear as a firm, red nodule, or as a rough, scaly flat lesion that may bleed and become crusty. Both basal cell and squamous cell cancers mainly occur on areas of the skin frequently exposed to the sun, but can occur anywhere.

• Melanoma usually appears as a pigmented patch or bump. It may resemble a normal mole, but usually has a more irregular appearance.

When looking for melanoma, think of the ABCD rule that tells you the signs to watch for:

• Asymmetry - the shape of one half doesn't match the other

• Border - edges are ragged or blurred

• Color - uneven shades of brown, black, tan, red, white or blue

• Diameter - A significant change in size (greater than 6mm)

Skin cancers are named for the type of cells that become malignant (cancer). The three most common types are:

·  Melanoma: Melanoma begins in melanocytes (pigment cells). Most melanocytes are in the skin.
Melanoma can occur on any skin surface. In men, it's often found on the skin on the head, on the neck, or between the shoulders and the hips. In women, it's often found on the skin on the lower legs or between the shoulders and the hips.
Melanoma is rare in people with dark skin. When it does develop in people with dark skin, it's usually found under the fingernails, under the toenails, on the palms of the hands, or on the soles of the feet.

·  Basal cell skin cancer: Basal cell skin cancer begins in the basal cell layer of the skin. It usually occurs in places that have been in the sun. For example, the face is the most common place to find basal cell skin cancer.

In people with fair skin, basal cell skin cancer is the most common type of skin cancer.

·  Squamous cell skin cancer: Squamous cell skin cancer begins in squamous cells. In people with dark skin, squamous cell skin cancer is the most common type of skin cancer, and it's usually found in places that are not in the sun, such as the legs or feet.
However, in people with fair skin, squamous cell skin cancer usually occurs on parts of the skin that have been in the sun, such as the head, face, ears, and neck.