Basal cell carcinomas usually develop on sun-exposed parts of your body, especially your head and neck. A much smaller number occur on the trunk and legs. Yet basal cell carcinomas can also occur on parts of your body that are rarely exposed to sunlight.
Although a general warning sign of skin cancer is a sore that won't heal or that repeatedly bleeds and scabs over, basal cell cancer may also appear as:
- A pearly white or waxy bump, often with visible blood vessels, on your face, ears or neck. The bump may bleed and develop a crust. In darker skinned people, this type of cancer may be brown or black.
- A flat, scaly, brown or flesh-colored patch on your back or chest. Over time, these patches can grow quite large.
- More rarely, a white, waxy scar. This type of basal cell carcinoma is easy to overlook, but it may be a sign of a particularly invasive and disfiguring cancer called morpheaform basal cell carcinoma.
When to see a doctor
Make an appointment with your doctor if you have any signs or symptoms that worry you.
Basal cell carcinoma occurs when one of the skin's basal cells develops a mutation in its DNA. Basal cells are found at the bottom of the epidermis — the outermost layer of skin. Basal cells produce new skin cells. As new skin cells are produced, they push older cells toward the skin's surface, where the old cells die and are sloughed off.
The process of creating new skin cells is controlled by a basal cell's DNA. A mutation in the DNA causes a basal cell to multiply rapidly and continue growing when it would normally die. Eventually the accumulating abnormal cells may form a cancerous tumor.
Ultraviolet light and other causes
Much of the damage to DNA in basal cells is thought to result from ultraviolet (UV) radiation found in sunlight and in commercial tanning lamps and tanning beds. But sun exposure doesn't explain skin cancers that develop on skin not ordinarily exposed to sunlight. This indicates that other factors may contribute to your risk of skin cancer, such as being exposed to toxic substances or having a condition that weakens your immune system.
Factors that increase your risk of basal cell carcinoma include:
- Chronic sun exposure. A lot of time spent in the sun — or in commercial tanning booths — increases the risk of basal cell carcinoma. The threat is greater if you live in a sunny or high-altitude climate, both of which expose you to more UV radiation. The risk is also higher if most of your exposure occurred before the age of 18. Your risk is greater if you have had at least one blistering sunburn.
- Exposure to radiation. Psoralen plus ultraviolet A (PUVA) treatments for psoriasis may increase your risk of basal cell carcinoma and other forms of skin cancer. Having undergone radiation treatments for childhood acne or other conditions also may increase your risk of basal cell carcinoma.
- Fair skin. If you have very light skin or you freckle or sunburn easily, you're more likely to develop skin cancer than is someone with a darker complexion. Basal cell carcinoma is rare in black people.
- Your sex. Men are more likely to develop basal cell carcinoma than women are.
- Your age. Because basal cell carcinomas often take decades to develop, the majority of basal cell carcinomas occur in people age 50 or older.
- A personal or family history of skin cancer. If you've had basal cell carcinoma one or more times, you have a good chance of developing it again. If you have a family history of skin cancer, you may have an increased risk of developing basal cell carcinoma.
- Immune-suppressing drugs. Taking medications that suppress your immune system, especially after transplant surgery, significantly increases your risk of skin cancer. Cancers in people with a weakened immune system generally are more aggressive than they are in otherwise healthy people.
- Exposure to arsenic. Arsenic, a toxic metal that's found widely in the environment, increases the risk of basal cell carcinoma and other cancers. Everyone has some arsenic exposure because it occurs naturally in the soil, air and groundwater. But people who may be exposed to higher levels of arsenic include farmers, refinery workers, and people who drink contaminated well water or live near smelting plants.
- Inherited syndromes that cause skin cancer. Certain rare genetic diseases increase the risk of basal cell carcinoma. Nevoid basal cell carcinoma syndrome (Gorlin-Goltz syndrome) causes numerous basal cell carcinomas, as well as pitting on the hands and feet and spine abnormalities. Xeroderma pigmentosum causes an extreme sensitivity to sunlight and a high risk of skin cancer because people with this condition have little or no ability to repair damage to the skin from ultraviolet light.
Complications of basal cell carcinoma can include:
- A risk of recurrence. Basal cell carcinomas commonly recur. Even after successful treatment, they may recur, often in the same place.
- An increased risk of other types of skin cancer. A history of basal cell carcinoma may also increase the chance of developing other types of skin cancer, such as squamous cell carcinoma and melanoma.
- Cancer that spreads beyond the skin. Rare, aggressive forms of basal cell carcinoma can invade and destroy nearby muscles, nerves and bone. Very rarely, basal cell carcinoma can spread to other areas of the body.
You may reduce your risk of basal cell carcinoma if you:
- Avoid the midday sun. Avoid the sun when its rays are the strongest. For most places, this is between about 10 a.m. and 4 p.m. Because the sun's rays are strongest during this period, try to schedule outdoor activities for other times of the day, even in winter. You absorb UV radiation year-round, and clouds offer little protection from damaging rays.
- Use sunscreen year-round. Choose a sunscreen that blocks both UVA and UVB types of radiation from the sun and has an SPF of at least 15. Apply sunscreen generously, and reapply every two hours — or more often if you're swimming or perspiring. The American Academy of Dermatology recommends using a broad-spectrum sunscreen with an SPF of 30 or more. Even the best sunscreen might be less effective than the SPF number on the bottle would lead you to believe if it isn't applied thoroughly or thickly enough, or if it's perspired away or washed off while swimming.
- Wear protective clothing. Wear protective clothing. Sunscreens don't provide complete protection from UV rays, so wear tightly woven clothing that covers your arms and legs, and a broad-brimmed hat, which provides more protection than a baseball cap or visor does. Some companies also sell photoprotective clothing. And don't forget sunglasses. Look for a pair that provides full protection from both UVA and UVB rays.
- Avoid tanning beds. Tanning beds emit UV radiation, which can increase the risk of skin cancer.
- Become familiar with your skin so that you'll notice changes. Examine your skin so that you become familiar with what your skin normally looks like. This way, you may be more likely to notice any skin changes. With the help of mirrors, check your face, neck, ears and scalp. Examine your chest and trunk, and the tops and undersides of your arms and hands. Examine both the front and back of your legs, and your feet, including the soles and the spaces between your toes. Also check your genital area, and between your buttocks. If you notice anything unusual, point it out to your doctor at your next appointment.
- Ask your doctor about screening. If you've already had skin cancer, you have an increased risk of a second cancer. Talk with your dermatologist about how often you should be screened for a recurrence and whether you should do periodic skin checks on your own.