Listen to the Cancer.Net Podcast: Protecting Your Skin From the Sun, adapted from this feature.

Warmer weather often means more time is spent outdoors in the sun. The month of May is designated as Skin Cancer Prevention and Detection Month to remind everyone to limit sun exposure to the skin to prevent skin cancer. While skin cancer is the most common of all cancers, most types of skin cancer can be prevented by reducing exposure to ultraviolet (UV) radiation from sunlight.

Types of skin cancer

There are three main types of skin cancer, which are named after the cells in which each begins.

Basal cell carcinoma

Basal cell carcinoma (BCC) is the most common type of skin cancer, with more than 800,000 cases diagnosed each year in the United States. The basal cells lie at the bottom of the epidermis, which is the outer layer of skin.

People with fair skin, light hair, and blue eyes are at a higher risk for developing BCC, as are those with occupations that require a great deal of outdoor time.

BCC may appear as an open sore that bleeds or oozes, a reddish patch, a shiny bump with a pearly look, a pinkish growth, or a scar-like area. Since BCC is linked with sun exposure, it is usually found on areas of the skin that receive the most sun, such as the face, ears, neck, scalp, shoulders, and back.

Squamous cell carcinoma

Squamous cell carcinoma (SCC) is the second most common type of skin cancer. Squamous cells are flat cells that make up most of the epidermis. Approximately 200,000 people in the United States are diagnosed with SCC annually. Even though SCC can start in any area of the body, it is most common in areas that are exposed to the sun.

SCC can invade underlying structures if it is not treated and may cause serious health problems or even death.

As with BCC, the most common cause of SCC is exposure to the sun. Similarly, people with fair skin, light hair, and blue eyes are at a higher risk for developing SCC than people with darker skin and features.

SCC may look like a wart-like growth that crusts or bleeds, a persistent scaly red patch with irregular borders, an open sore that doesn't heal, or an elevated growth that may crust or bleed.

Melanoma

Melanoma is the most serious type of skin cancer. Melanoma can be successfully treated in almost all cases if it is found early. However, melanoma can spread to other parts of the body and can be difficult to treat successfully at later stages. About 60,000 new melanoma cases will be diagnosed in the United States in 2007.

Melanoma is a malignant (cancerous) tumor arising from the melanocytes, which are the cells that produce melanin, the pigment in the skin. Therefore, melanoma is usually black or dark brown due to the melanin, but it can also be de-pigmented, leaving the growth pinkish or white. Most melanomas have irregular borders and appear asymmetrical (not the same on both sides).

Again, sunlight exposure is a major risk factor. Melanoma is found most frequently on the backs of men and women and on the legs of women, but it can occur anywhere on the body.

Sun protection tips

Most skin cancer is caused by sun exposure. Therefore, limiting the amount of sun exposure to the skin is the best way to prevent skin cancer.

• Use a sunscreen with a sun protection factor (SPF) of 15 or higher every day. Apply liberally 20 minutes before going outdoors and reapply every two hours and after swimming or sweating, as most sunscreens will wash off.

• Use extra caution near water, snow, and sand, as they reflect the damaging rays of the sun. This can increase the chance of sunburn.

• Limit sun exposure from 10:00 AM – 4:00 PM, which is when the sun's rays are the most intense. Practice the shadow rule: if your shadow is shorter than you, the sun's rays are at their strongest, and you should find shade.

• Protect your skin with a long-sleeved shirt, long pants, and a hat that shades the face, neck, and ears. Dark clothing with tightly woven fabric blocks more sun than white or loosely woven fabrics. For additional protection, look for clothing made with special sun-protective materials.

• Wear sunglasses with 99% to 100% UV absorption to provide optimal protection for the eyes and the surrounding skin.

• Pay attention to the UV index, which is often included in the weather report. This index is a relative measure of how damaging exposure to the sun will be on any particular day. The index is a scale of 1 to 10+. When the index is 10 or higher, it usually is recommended that people stay indoors if possible.

• Never use tanning beds or sunlamps.

It is important to examine your skin each month to look for new growths or changes in the appearance of existing ones. Often, the first sign of melanoma is a change in the size, shape, or color of an existing mole. It also may appear as a new or abnormal-looking mole. The "ABCDE" rule can help remember what to watch for.

Asymmetry: The shape of one half of the mole does not match the other.

Border: The edges are ragged, notched, or blurred.

Color: The color is often uneven. Shades of black, brown, and tan may be present. Areas of white, gray, red, or blue may also be seen.

Diameter: The diameter is usually larger than six millimeters (mm) (the size of a pencil eraser) or has grown in size.

Evolving: The mole has been changing in size, shape, color, appearance, or growing in an area of previously normal skin. Also, when melanoma develops in an existing mole, the texture of the mole may change and become hard, lumpy, or scaly. Although the skin may feel different and may itch, ooze, or bleed, melanoma usually does not cause pain.

Regular self-examinations may help find skin cancer early. Examinations should be performed in front of a full-length mirror in a brightly lit room. It helps to have another person check the scalp and back of the neck. Most moles are not cancerous. But if you notice a mole that is changing, be sure to have it checked by a dermatologist. And, people at high risk for skin cancer should have their skin examined once a year by a dermatologist. If detected early, most skin cancer can be successfully treated.

Additional resources

American Cancer Society (ACS): Skin Cancer Facts

The Skin Cancer Foundation

SkinCancerNet (a comprehensive online skin cancer information resource from the American Academy of Dermatology [AAD])

U.S. Environmental Protection Agency SunWise Program