What is Skin Cancer?
Skin cancer is the most common cancer in the United States. In fact, more skin cancers are diagnosed in the US each year than all other cancers combined. The number of skin cancer cases has been going up over the past few decades.
The good news is that you can do a lot to protect yourself and your family from skin cancer, or catch it early so that it can be treated effectively. Most skin cancers are caused by too much exposure to ultraviolet (UV) rays. Most of this exposure comes from the sun, but some may come from man-made sources, such as indoor tanning beds and sun lamps.
You don’t need any x-rays or blood tests to find skin cancer early — just your eyes and a mirror. If you have skin cancer, finding it early is the best way to make sure it can be treated with success.
Skin cancer starts in the cells of the skin. Some other types of cancer start in other parts of the body and can spread to the skin, but these are not skin cancers.
There are 3 main types of skin cancers:
- Basal cell skin cancers (basal cell carcinomas)
- Squamous cell skin cancers (squamous cell carcinomas)
Basal and Squamous Cell Cancers
Basal and squamous cell skin cancers are by far the most common cancers of the skin. Both are found mainly on parts of the body exposed to the sun, such as the head and neck. These cancers are strongly related to a person’s sun exposure.
Basal and squamous cell cancers are much less likely than melanomas to spread to other parts of the body and become life threatening. Still, it’s important to find and treat them early. If left alone, they can grow larger and invade nearby tissues and organs, causing scarring, deformity, or even loss of function in some parts of the body. Some of these cancers (especially squamous cell cancers) can spread if not treated, and in some cases they can even be fatal.
Melanomas are cancers that develop from melanocytes, the cells that make the brown pigment that gives skin its color. Melanocytes can also form benign (non-cancerous) growths called moles. (Your doctor might call the mole a nevus.)
Melanomas can occur anywhere on the body, but are more likely to start in certain areas. The trunk (chest and back) is the most common place in men. In women, the legs are the most common site. The neck and face are other common places for melanoma to start.
Melanomas are not as common as basal cell and squamous cell skin cancers, but they can be far more serious. Like basal cell and squamous cell cancers, melanoma is almost always curable in the early stages. But if left alone, melanoma is much more likely to spread to other parts of the body, where it can be very hard to treat.
Other Skin Cancers
There are many other types of skin cancers as well, but they are much less common:
- Merkel cell carcinoma
- Kaposi sarcoma
- Cutaneous (skin) lymphoma
- Skin adnexal tumors (tumors that start in hair follicles or sweat and oil glands)
Together, these types account for less than 1% of all skin cancers.
It’s important for doctors to tell the types of skin cancer apart, because they are treated differently. It’s also important for you to know what skin cancers look like. This can help you find them at the earliest possible stage, when they are cured most easily.
Regular skin exams are especially important for people who are at higher risk of skin cancer, such as people with reduced immunity, people who have had skin cancer before, and people with a strong family history of skin cancer. Talk to your doctor about how often you should have your skin examined.
Get Your Skin Checked Early
Your doctor should check your skin carefully as part of a routine cancer-related check-up. They should be willing to discuss any concerns you might have about this exam.
Check Your Own Skin
It’s important to check your own skin, preferably once a month. A skin self-exam is best done in a well-lit room in front of a full-length mirror. You can use a hand-held mirror to look at areas that are hard to see, such as the backs of your thighs. A spouse or close friend or family member may be able to help you with these exams, especially for those hard-to-see areas like your back or scalp.
The first time you examine your skin, spend time carefully going over the entire surface. Learn the patterns of moles, blemishes, freckles, and other marks on your skin so that you’ll notice any changes next time. Be sure to show your doctor any areas that concern you.
What is Ultraviolet (UV) Radiation?
Exposure to ultraviolet (UV) radiation is a major risk factor for most skin cancers. Sunlight is the main source of UV rays. Tanning lamps and beds are also sources of UV rays. People who get a lot of UV exposure from these sources are at greater risk for skin cancer.
Even though UV rays make up only a very small portion of the sun’s rays, they are the main cause of the sun’s damaging effects on the skin. UV rays damage the DNA of skin cells. Skin cancers start when this damage affects the DNA of genes that control skin cell growth.
There are 3 main types of UV rays:
- UVA rays age skin cells and can damage their DNA. These rays are linked to long-term skin damage such as wrinkles, but they are also though to play a role in some skin cancers. Most tanning beds give off large amounts of UVA, which has been found to increase skin cancer risk.
- UVB rays have slight more energy than UVA rays. They can damage skin cells’ DNA directly, and are the main rays that cause sunburns. They are also thought to cause most skin cancers.
- UVC rays have more energy than the other types of UV rays, but they don’t get through our atmosphere and are not in sunlight. They are not normally a cause of skin cancer.
Both UVA and UVB rays can damage skin and cause skin cancer. UVB rays are a more potent cause of at least some skin cancers, but based on what’s known today, there are no safe UV rays.
The strength of the UV rays reaching the ground depends on a number of actors, such as:
- Time of day: UV rays are strongest between 10 am and 4 pm.
- Season of the year: UV rays are stronger during spring and summer months. This less of a factor near the equator.
- Distance from the equator (latitude): UV exposure goes down as you get further from the equator.
- Altitude: More UV rays reach the ground at higher elevations.
- Cloud cover: The effect of clouds can vary. Sometimes cloud cover blocks some UV from the sun and lowers UV exposure, while some types of clouds can reflect UV and can increase UV exposure. What is important to know is that UV rays can get through, even on a cloudy day.
- Reflection off surfaces: UV rays can bounce off surfaces like water, sand, snow, pavement, or grass, leading to an increase in UV exposure.
The amount of UV exposure a person gets depends on the strength of the rays, the length of time the skin is exposed, and whether the skin is protected with clothing or sunscreen.
People who live in areas with year-round, bright sunlight have a higher risk of skin cancer. Spending a lot of time outdoors for work or recreation without protective clothing and sunscreen increases your risk.
The pattern of exposure may also be important. For example, frequent sunburns in childhood may increase the risk for some types of skin cancer many ears or even decades later.
Skin cancers are one result of getting too much sun, but there are other effects as well. Sunburn and tanning are the short-term results of too much exposure to UV rays, and are signs of skin damage. Long-term exposure can cause early skin aging, wrinkles, loss of skin elasticity, dark patches (lentigos, sometimes called age spots or liver spots), and pre-cancerous skin changes (such as dry, scaly, rough patches called actinic keratosis).
The sun’s UV rays increase a person’s risk of cataracts and certain other eye problems, too. They can also suppress the skin’s immune system. Darker-skinned people are generally less likely to get skin cancer than light-skinned people, but they can still get cataracts and immune suppression.
The UV Index
As noted above, the amount of UV light reaching the ground in any given place depends on a number of actors, including the time of day, time of year, elevation, and cloud cover. To help people better understand the strength of UV light in their area on a given day, the National Weather Service and the Environmental Protection Agency (EPA) have developed the UV Index. It gives people an idea of how strong the UV light is in their area, on a scale from 1 to 11+. A higher number means greater risk of exposure to UV rays and a higher chance of sunburn and skin damage that could ultimately lead to skin cancer.
The UV Index is given daily for regions throughout the country. Many newspapers, television, online, and smartphone weather forecasts include the projected UV Index. Further information about the UV Index, as well as your local UV Index forecast, can be found on the EPA’s website at www.epa.gov/sunwise/uvindex.html. Smartphone apps are available from the EPA at www.epa.gov/enviro/mobile. As with any forecast, local changes in cloud cover and other factors could change the actual UV levels experiened.
Are Some People More Likely to Get Skin Damage from the Sun?
Everyone’s skin and eyes can be affected by the sun and other forms of ultraviolet (UV) rays. People with light skin are much more likely to have sun damage, but darker-skinned people, including people of any ethnicity, can also be affected.
For some people, the skin tans when it absorbs UV rays. The tan is caused by an increase in the activity and number of melanocytes, the cells that make the pigment melanin. Melanin helps block out damaging UV rays up to a point, which is why people with naturally darker skin are less likely to get sunburned, while people with lighter skin are more likely to burn. Sunburns can increase your risk of skin cancer, including melanoma. But UV exposure can raise skin cancer risk even without causing sunburn.
Aside from skin tone, other factors can also affect your risk of damage from UV light. You need to be especially careful in the sun if you:
- Had skin cancer before
- Have a family history of skin cancer, especially melanoma
- Have many moles, irregular moles, or large moles
- Have freckles and burn before tanning
- Have fair skin, blue or green eyes, or blond, red, or light brown hair
- Live or vacation at high altitudes (the strength of UV rays increases the higher up you are)
- Live or vacation in tropical or subtropical climates
- Work indoors all week and then get intense sun exposure on weekends
- Spend a lot of time outdoors
- Have certain autoimmune disease, such as systemic lupus erythematosus (SLE, or “lupus”)
- Have certain inherited conditions that increase your risk of skin cancer, such as xeroderma pigmentosum (XP) or nevoid basal cell carcinoma syndrom (Gorlin syndrome)
- Have a medical condition that weakens your immune system, such as infection with HIV (the virus that causes AIDS)
- Have had an organ transplant
- Take medicines that lower or suppress your immune system
- Take medicines that make your skin more sensitive to sunlight
Ask your doctor, nurse, or pharmacist if you are taking any medicines that could increase your sensitivity to sunlight.