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5.5: The Basics of Skin Cancer

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    Learning Objectives
    • To distinguish between the different types of ultraviolet radiation.
    • To interpret the ABCDE's of skin cancer.
    • Compare the three types of skin cancer.
    • Identify ADA-recommended skin care products (i.e.- SPF, Broad Spectrum terminology)
    • Recall how often sun protection products should be applied.  
    • Explain the difference between water resistant and waterproof.
    • Identify ADA-recommended UPF clothing.

    Exposure to Ultraviolet Radiation

    Of all the types of ionizing radiation, people come into more contact with ultraviolet radiation. Sources of this radiation would include the sun, ultraviolet lights, and tanning beds. The sun produces three different forms of ultraviolet rays (UVA, UVB, and UVC). Fortunately, the deadliest of these three rays (UVC) never reaches the earth's surface and is absorbed by the Earth's ozone layer. However, both UVA and UVB reach the Earth's surface to affect living systems.

    Diagram titled "When looking for a sunscreen that will protect you from UVB and UVA rays." SPF with broad spectrum protects against UVB and UVA rays. SPF only refers to protecting against UVB rays. UVB causes sunburns, UVA causes suntans. Both UVB and UVA cause cancer and early skin aging.
    Figure \(\PageIndex{1}\): Effect of Light on skin

    UVA is produced naturally by the sun and artificially by lamps and tanning beds. For years, sunbathers believed that UVA provided only a youthful glow. Now, the American Academy of Dermatologists has condemned the use of tanning beds. Scientific research has correlated certain types of skin cancers (mainly basal and squamous cell) with the use of these devices. Besides skin cancer, tanning beds cause premature aging and damage to your eyes. If a tanning bed is not properly sanitized between uses, skin diseases can be transmitted from one consumer to another.

    Recognizing Suspicious Skin Changes

    According to the American Academy of Dermatologists, skin cancer is the most common form of cancer. Exposure to ultraviolet rays or arsenic can cause skin diseases. Additionally, some individuals may be genetically predisposed to developing this illness (check out your family tree). Approximately 10,000 Americans a day will be diagnosed with one of the three different forms of skin cancer. Millions of Americans have already been diagnosed with the most common form of skin cancer, basal cell carcinoma. This type of cancer grows very slowly and can spread to other parts of the body. Basal cell carcinoma frequently appears on the head and neck of a patient. Rarely, basal cell carcinoma can eventually affect other areas of the body like skin or bone.

    The ABCDE's stand for asymmetry, border, color, diameter, and evolving. Normal moles are symmetrical, has even borders, are one color, smaller than 1/4 inch, and do not change. Melanoma is seen in moles that are asymmetrical, has uneven borders, multiple colors, are larger than 1/4 inch, and change in size/shape/color.
    Figure \(\PageIndex{2}\): ABCDEs of Skin Cancer. A brown spot on the skin is likely to be a harmless mole, but it could be a sign of skin cancer. Unlike moles, skin cancers are generally asymmetrical, have irregular borders, may be very dark in color, and may have a relatively great diameter.

    Squamous cell carcinoma appears more commonly on the face, neck, lips, and hands of the person. For females, squamous typically presents on the lower leg portion. This form of skin cancer is more likely to metastasize (spread) than basal cell carcinoma. If caught early and treated, patients can easily survive both basal and squamous cell carcinomas.

    Melanoma, the most serious form of skin cancer, is the least common of all skin cancers. This type of cancer usually manifests on the trunks of males and the legs of females. It can spread easily to the brain, liver, bones, abdomen, or lymph nodes. If detected early, survival rates are good and life expectancy will be normal.

    Figure \(\PageIndex{2}\) compares normal pigmentations to moles that have changed into melanoma. Monthly reviews of skin lesions and seeking medical advice is key to surviving this disease. Be sure to note these visual characteristics (the ABCDEs) of skin cancer for future evaluations (life and class).

    Sunblocks and Sunscreens

    UVB radiation in sunlight allows the skin to produce vitamin D. This vitamin prevents bone disorders like rickets and osteoporosis (brittle bone disease). The American Academy of Dermatology suggests vitamin D be obtained through foods or nutritional supplements. Excessive exposure to UV can be damaging and the pigment melanin, deposited in cells at the base of the epidermis, helps to protect the underlying layers of the skin from this damage. Melanin also colors the skin and variations in the amount of melanin produces colors from pale yellow to black. The darker the skin tone, the more melanin one has, and the less likely skin cancer will occur.

    Figure \(\PageIndex{3}\): The author's great, great- grandmother was diagnosed with skin cancer on her nose during the 1950's.

    Excess exposure to the sun can cause sunburn. This is common in humans, but light skinned animals like cats and pigs can also be sunburned, especially on the ears. Skin cancer can also result from excessive exposure to the sun. As holes in the ozone layer increase exposure to the sun’s UV rays, so too does the rate of skin cancer in humans and animals.

    Sunscreens and sunblocks are designed to protect skin from ultraviolet rays. Sunblocks contain inorganic ingredients like zinc oxide or titanium dioxide. These chemicals act as UV filters by reflecting the sun's UV rays. Sunblocks can have grainy textures due to the inorganic components. The thick nature of a sunblock can make it difficult to spread evenly on the skin. Sunscreens contain organic compounds like oxybenzone, avobenzone, homosalate, and octinoxate (Figure \(\PageIndex{4}\)). By absorbing ultraviolet rays, these compounds decompose and give off heat. Sunscreens apply smoother than sunblocks. Often, manufacturers will combine sunscreen and sunblock ingredients to make their products.

    Diagram of the chemistry of sunscreen. Inorganic in sunscreen, such as zinc oxide and titanium oxide, both absorb and scatter UV light. Organic chemicals are also used - the chemical bonds in these absorb UV radiation, with the chemical structure affecting whether they absorb UVA, UVB, or both. Several different chemicals are used in sunscreen to ensure full protection.
    Figure \(\PageIndex{4}\): Effect of Light on skin

    Sun protection factor (SPF) measures a product's protection from UVB rays. SPF does not quantify protection from UVA radiation. The American Academy of Dermatology recommends you select a sunscreen or sunblock with a minimum SPF factor of 30. This SPF value means a lotion can filter out 97% of UVB rays. Moving to a SPF of 50 will only filter out 1 more percentage of UVB rays. Increasing an SPF factor past 30 does very little in shielding skin from UVB radiation.

    Products that protect skin from UVA must be labeled as being a broad spectrum. Sunblocks provide UVA and UVB protection, but sunscreens can vary on what they can screen. Every two hours, sunscreens/sunblocks should be reapplied to the skin. Sweating and swimming can remove sunscreen/sunblock products. No sun products are waterproof, but some are labeled as being water-resistant. Consumers are encouraged to reapply these products every two hours as well.

    Clothing and Other Pgarments

    Though most people are unaware, the clothing they wear every day serves as a barrier against harmful ultraviolet rays. The garment Ultraviolet Protection Factor (UPF) of a material is measured by how much UVA and UVB rays come in contact with the skin. Garments that receive a good rating by the Skin Cancer Foundation's Seal of Recommendation have a UPF rating of at least 30. Fabrics that receive excellent ratings have UPF values of 50 and can block 98% of the sun's rays, allowing only 2% to penetrate the skin.

    Video \(\PageIndex{1}\): Labor Day skincare tips: UPF clothing. Whether you’re heading to the UT football game or having a cookout by the pool, it’s important to protect your skin from the sun, and sunscreen isn’t the only way you can do that. Dr. Kellie Reed with Sanovseven specific factors maket UPF clothing.

    Clothing does not protect equally and seven specific factors make clothing more effective: UPF, color, construction, content, fit, coverage, and activity. Contrary to lighter shades, darks, and bright colors absorb UV rays rather than letting them penetrate your skin. Densely woven clothing, like denim, wool, or synthetic fibers is more beneficial than tight clothing. If clothing becomes stretched, thinner, or wet, UV rays can seep through the fabric. Therefore, the thicker and looser the clothing, the more protection it will provide for the skin. Shiny polyester and lightweight silk fabrics are highly protective because they reflect radiation. Other fabrics like unbleached cotton and high-tech fabrics treated with chemical UV absorbers or dyes are also effective in shielding skin from UV exposure.

    When spending large amounts of time outside, wearing long-sleeved shirts and pants offers more protection of skin. Topping off your outfit with a wide-brimmed hat maximizes protection from UV rays and helps prevent basal and squamous cancers that often appear on the head and neck and account for 90% of skin cancers. Lastly, select sunglasses that have been certified to protect your eyes from UV rays. A good pair of sunglasses will reduce your risk of developing cataracts later in life.

    Contributors and Attributions

    This page titled 5.5: The Basics of Skin Cancer is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Elizabeth Gordon.

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