Julia Draznin Maltzman, MD
Updated by Lara Bonner Millar, MD
The Abramson Cancer Center of the University of Pennsylvania
Ultima Vez Modificado: 27 de octubre del 2014
Sun (UVA and UVB rays) exposure can predispose to all types of skin cancers (melanoma, basal cell and squamous cell cancers). According to the most recent estimates, skin cancer is the most common type of cancer in the United States. At least 50% of all individuals aged 65 or greater have had at least one episode of skin cancer.
Skin cancer is certainly more common in people with light-colored skin, hair, and eyes, but dark-skinned individuals should not think that they are immune. Dark skin has a better ability to protect itself from the sun than light skin, but it too can become hyperpigmented and develop skin cancer. Experts say that this is particularly true after an outbreak of acne, eczema, or any other inflammatory process. Dermatologists advise darker-skinned patients to use sunscreen with an SPF of 15 or greater every day. Having said this, melanomas in darker-skinned individuals actually tend to occur in areas that are not exposed to sun, such as buttocks, genitals, bottom of the feet, and under the fingernails or toenails.
Skin cancer can occur anywhere on the body. It is most commonly seen in places that have received the most sun exposure, such as the face, neck, hands and arms. However, as mentioned above, skin cancer can be seen in areas that don't receive much, if any sun exposure. Remember, skin cancer seldom causes pain, itching, or other symptoms, so meticulous examination of the skin is the best way to screen for early cancers. Skin cancer can look different, depending on the skin type, site of disease, and type of cancer. The most common sign of skin cancer is a change on the skin; for example a change in color, a growth, a non-healing ulcer, a lump. Of course, one's skin goes through many changes over our lifetime, and most of these changes are not cancerous, but any changes should be called to the attention of a healthcare provider.
There are three types of skin cancers, melanoma, basal cell and squamous cell cancers. Basal cell carcinoma and squamous cell carcinoma are sometimes lumped together as the "non-melanoma skin cancers."
The most serious and least common type of skin cancer is melanoma, which arises in the pigmented cells called melanocytes. However, if melanoma is diagnosed and removed while it is limited to the outermost skin layer, it is almost 100% curable. Once it has metastasized (spread to other areas of the body), it is a much more difficult disease to treat.
Several studies have shown that sunburns early in life are associated with a greater risk of developing melanoma than sunburns that occur later in the adult years. However, sunburns at any age can increase the individual's risk to develop skin cancer. Unlike other skin cancers, melanoma has a hereditary component. Any person with a family history of melanoma should be examined regularly by a healthcare provider, as well as perform his/her own skin checks, because early detection is essential.
Melanoma most often arises from a pre-existing mole or pigmented lesion, therefore any change in an existing mole should be examined by a healthcare provider. In general, a normal mole is solid-colored with well-defined edges, and a round or oval shape. When examining the skin, look for the A-B-C-D-E's.
These are guidelines, and not every mole that has one or more of these qualities will be found to be cancerous. In addition, not every cancer has these characteristics. This is why it is important to examine your skin regularly and get to know your moles, so that you can identify any changes in them. Any change in a mole should be examined by a healthcare provider.
The most common form of skin cancer is called basal cell carcinoma (BCC), which accounts for about 90% of skin cancers in the United States. These cancers arise in the basal cells, the cells at the bottom-most layer of the outer skin (called the epidermis). This type of cancer rarely metastasizes, although it can invade lymph nodes and blood vessels. This type of cancer primarily spreads locally and invades surrounding tissue. Depending on the location of the cancer, it can lead to severe disfigurement.
Another common type of skin cancer is called squamous cell carcinoma (SCC). These cells are derived from the outer-most layers of the skin. Like BCC, it can spread locally and invade surrounding organs or tissues; and like melanoma, it can metastasize to other parts of the body if left untreated.
Both BCC and SCC occur most often in areas of the body that have heavy, chronic sun exposure, though they can occur elsewhere. People who have had extensive sun exposure in their lifetime should examine their skin regularly for any signs of pre-cancerous or cancerous skin lesions.
Most skin cancers develop after the age of 50, however the damaging effects of the sun begin in childhood. In a study by the FDA, (Food and Drug Administration) it was noted that most Americans receive 25% of their lifetime sun exposure before the age of 18. Furthermore, several studies have shown that sunburns early in life are associated with a greater risk of developing melanoma than sunburns later in the adult years. However, sunburns at any age can increase the individual's risk to develop skin cancer. It is not only acute sunburns that predispose to skin cancer, as chronic sun exposure can add up and cumulative sun toxicity is also associated with the development of this disease. In addition, tanning booths are a big concern, particularly for teens, and are a likely cause of the increase in cases in women in their 20s.
Protecting yourself against the sun's damage is the best prevention for skin cancer. One of the easiest ways to protect yourself is to avoid exposure when the sun's rays are the strongest, from 10am to 3pm. Wearing protective clothing such as a hat, long sleeves and sunglasses can block out some of the sun's harmful rays. Tanning booths should be avoided, as they are not a safe alternative to the sun.
Sunscreen should be used everyday, even in the winter. There are many sunscreens to choose from. Experts recommend using a sunscreen that protects against UVA and UVB rays, as both cause skin damage and can lead to cancer. These products are labeled "broad spectrum". There are two different forms of sunscreen; physical and chemical:
There are hundreds of varieties of sunscreen available now, and choosing among them may be a daunting task. Here are a few guidelines. No one sunscreen can offer 100% protection from the UV rays. Even with sunscreen, UV radiation can penetrate through the top few layers of skin. Therefore, most dermatologists recommend using sunscreen with other forms of protection such as clothing, hats, and shade. However, keep in mind that clothing also cannot protect the skin fully, as the sun's rays can penetrate it.
The SPF in sunscreens stands for Sun Protection Factor, and offers protection from the UV sunrays. SPF of 30 or greater offers the maximum protection from the sun by blocking 96% of UV light, whereas sunscreen with SPF of 15 will block out 93% of all UV rays. It is a misconception that SPF of 15 blocks only half the amount of sun that an SPF of 30 does. An expert dermatologist explained that an SPF of 30 allows an individual to stay out in the sun twice as long as an SPF of 15 with the same protection. By extension, applying one coat of a sunscreen that has 30 SPF on top of another sunscreen that has 15 SPF does NOT result in SPF of 45. In fact, the result of the mixture is a dilution of the stronger SPF, and thus lowers the overall protection offered.
Experts agree that sunscreen should be applied every two hours and after swimming, excessive sweating, and showering. Manufacturers are no longer allowed to say a product is "waterproof" or "sweatproof". They now have to tell you how long it can last if you are wet or sweaty; the labeling will now read "water resistant" to 40 minutes or 80 minutes. That gives you guidance of when to reapply; however, you should always reapply after 2 hours as it becomes unactive at that point.
Sunscreen should be applied 15 to 20 minutes prior to going out into the sun to allow it to soak into the deeper layers of the outer skin before exposure. On average, an adult should use about two tablespoons of sunscreen for a single application (about a shot glass full). Recent evidence showed that most people get sun burned because they are not using enough sunscreen. One way to ensure adequate sun protection is to apply sunscreen and then reapply after twenty minutes. Check the expiration date of your sunscreen, since some ingredients may break down over time.
All experts agree, however, that limiting sun exposure time is by far the best method of sun protection one can follow. Self tanning lotions or sprays are a safe alternative to the sun, but remember that this does not give you protection, so you will still need to use SPF after tanning with these products.
Research in the US and Australia showed that sunrays have both Ultraviolet-A (UVA) and Ultraviolet-B (UVB) rays, which may play a bigger role in the development of cancer than originally believed. Traditionally, UVB rays were thought to be responsible for causing skin cancer. However, the effects of UVA may have been woefully underestimated. Researchers knew that UVA penetrated the skin more deeply than UVB. However, the belief was that UVA rays were less likely to be absorbed by the skin cells and therefore less likely to cause mutations in the cellular DNA. When scientists looked at the effects of UVA and UVB on the DNA from different skin cancer cells, they found that UVA in fact was responsible for many cancerous mutations. This finding has long been suspected in the dermatology world, but is now finally proven scientifically.
Dermatologists recommend using sunscreens that have both UVA and UVB protection ("broad spectrum"). Most sunscreens with SPF of 8 or greater will provide some UVA protection. To be certain, however, patients should look for parsol or benzophenones as key ingredients in sunscreens to ensure UVA protection.
Treatment for skin cancer almost always involves some type of surgery. In some cases, doctors can suggest radiation therapy or chemotherapy. In more advanced stages a combination of these modalities may be used.
The type of surgery used can vary depending on the dermatologist, lesion location, lesion characteristic and patient preference. Options include: curettage and electrodessication, Mohs' surgery, cryosurgery, or laser therapy. In severe case, skin grafting may be required.
Radiation therapy is used for the treatment of skin cancers if the location of the cancer is such that surgery would be too disfiguring. Such areas may include the eyelid, tip of nose, or ears.
Topical chemotherapy is used as anticancer drugs in the form of creams or lotions applied to the skin. These are often used for cancers limited to the top layers of the skin.
Sun exposure happens all year long, so make sun safety part of your daily routine and not something you only think about when you are heading to the beach. Remember, being sun-smart is being cancer-smart!