Skin cancer is one of the most common skin problems seen by dermatologists and the most common cause of skin cancers is exposure to ultraviolet light, found in sunlight and tanning beds. May has been designated as Skin Cancer Awareness Month and is an excellent time to talk about skin cancers and how to prevent them.
When a human goes out in the sunshine they may develop a sunburn, which is caused by an excess of ultraviolet B radiation (UVB). They also receive ultraviolet A (UVA) radiation at more moderate levels outside and through the windows of their car or in their home. Ultraviolet B light does not penetrate window glass, but UVA does. Both of these types of radiation damage the DNA in the cells near the surface of the skin, which can lead to brown spots, white spots, rough, precancerous lesions and skin cancer. UVA, in addition, penetrates much more deeply into the skin and causes a significant increase in wrinkles over time. Tanning beds use primarily UVA radiation, but at a much higher amount than in sunlight and is associated with both skin cancers and severe wrinkling.
The most common skin cancer is basal cell carcinoma (BCC), which comprises approximately one-quarter of all cancers in the U.S. Basal cells form from the outer layers of the skin, called the epidermis, and are almost always in areas that have had significant sun exposure. The older a person is, the greater their chance of developing a skin cancer, as they have increasing accumulated sun exposure.
Squamous cell carcinoma (SCC) is another common skin cancer caused by sun exposure, as well exposure to radiation treatment or chronic burn scars. These cancers are also from the epidermis of the skin, but the cells appear different from the BCC and they behave a little differently. Squamous cell carcinomas have a small risk of spreading to other areas of the body (metastasizing) such as the lymph nodes or other organs. There are precancerous growths that may warn of impending SCC development, and treatment of these growths can prevent SCC from occurring.
By far the worst of the common skin cancers is the malignant melanoma. This tumor of the pigment producing cells of the skin, called melanocytes, is significantly less common than the two previous cancers, but it is also by far the most aggressive and can potentially be fatal if not diagnosed and removed early. The thickness of the tumor (as measured by a tiny ruler under the microscope) correlates with the likelihood that a melanoma will spread. For example, a melanoma that it 1 millimeter (mm) thick will be less likely to spread to lymph nodes and organs such as the liver or brain than a melanoma that is 2 mm thick.
There are a number of precancerous growths that may turn into malignant melanoma. These may appear as moles that are growing or changing in appearance, especially if they are multicolored or have edges that are not smooth. There are also brown lesions of the skin that may look worrisome but are not at risk for melanoma. An alarming trend in skin cancers is the continuing increase in the number of new melanomas seen every year. Melanoma is increasing in all age groups, but the group that is increasing the fastest is women aged 18 to 29. This is also the group associated with the heaviest use of tanning beds.
Preventing skin cancers
How do you prevent skin cancers? The answer to this question is complex, but the most effective method is to limit your lifetime exposure to sunlight and tanning beds. Sun protection should begin at birth and continue throughout life.
Infants below the age of one year should be kept in the shade and should not use sunscreens below the age of six months, because of the sensitivity of their skin.
Children in the first three to four years of life should be protected with shade, hats, sun-protection swim suits and sunscreen. Studies suggest that intensive use of sunscreens in preschool age children may also decrease the number of moles that children develop.
The injuries to the skin that result in skin cancer include breaks in the chromosomes of the skin cells. The human body is able to correct such breaks, but the system is not perfect and the additive effect of sun exposure may eventually build up enough chromosome breakage that it cannot be repaired, and the character of the cell will change, becoming prone to the development of cancer, as well as the other changes in the skin that people dislike, such as wrinkles, brown spots, rough skin, red spots, etc.
When using sunscreen to protect the skin, select one that screens out both UVB and UVA. New Food and Drug Administration regulations, which will, hopefully, go into effect this year, require that sunscreens have similar levels of protection from both UVB and UVA. The Sun Protection Factor (SPF) of sunscreens indicates how much longer you can stay in the sun without burning, for example, an SPF of 30 suggests that you can stay out 30 times longer when using the sunscreen. This, however, is an approximation and was determined by testing with artificial lights in a cool room. The actual protection outdoors where it is hot and humid will vary considerably from this laboratory number.
To get the most from your sunscreen, you must apply it to all sun exposed areas 20 to 30 minutes before going outside. For most activities an SPF of 30 is sufficient, but you must reapply the sunscreen every two hours for continued protection with heat, sweating, swimming, etc. Protect your scalp, face, and ears with a hat that has a 4 to 5 inch brim all around. Do outside activities in the early morning and late evening to avoid the most intense sunlight.
Get checked out
All lesions that appear to be changing, growing, or look different than ordinary moles or spots, should be checked by your family doctor or a dermatologist. If the identity of the growth is not clear, a skin biopsy may be necessary for diagnosis. Most skin biopsies are very small pieces of skin, about half the size of a pencil eraser, and take only a few minutes to perform.
For more information on skin cancer and its prevention, go to The Skin Cancer Foundation website, at www.skincancer.org. The Foundation not only has extensive information on the appearance and treatment of skin cancers and pre-cancers, it has recommendations on sunscreens and other sun protective methods that have been tested to make sure that they work as advertised. Also watch for local skin cancer screenings and other health events.
Carey A. Bligard, M.D., is affiliated with UnityPoint Clinic Dermatology in Fort Dodge.