Causes, Risk Factors, and Prevention of Squamous Cell Carcinoma of the Skin

Exposure to UV rays is a major risk factor for most skin cancers, including SCC. Sunlight is the main source of UV rays. Tanning beds and sun lamps are also sources of UV rays.

Although UV rays make up a very small portion of the sun’s rays, they are the main cause of the damaging effects of the sun on the skin. UV rays damage the DNA (genes) inside skin cells. Skin cancers can begin when this damage affects genes that control skin cell growth.

To learn more about UV exposure and what you can do to protect yourself and your loved ones, see:

• UV (Ultraviolet) Radiation and Cancer Risk
• How to Protect Yourself from UV Rays

Anyone can get skin cancer, but people with lighter skin tones have a much higher risk than people with naturally darker skin tones. This is because melanin (skin pigment) has a protective effect in people with darker skin.

People are at especially high risk if they have skin that freckles or burns easily, blue or green eyes, or naturally red or blonde hair.

The risk of getting SCC rises as people get older. This is probably because years of sun exposure can lead to a buildup of gene changes in skin cells. But these cancers are becoming more common in younger people as well, probably because they are spending more time in the sun with their skin exposed.

Men are more likely than women to get SCC, likely because they tend to get more sun exposure.

Being exposed to large amounts of arsenic increases the risk of developing skin cancer, including SCC. Arsenic is an element found naturally in well water in some areas. It’s also used to make some pesticides and other substances.

Workers exposed to coal tar, paraffin, and certain types of petroleum products might also have an increased risk of SCC.

People who have had radiation treatment have a higher risk of developing skin cancer, including SCC, in the area where the radiation was focused. This is particularly a concern in children who have had radiation treatment for cancer.

People who have had a squamous cell carcinoma or another type of skin cancer have a much higher chance of developing another one.

Although the risk is small, squamous cell skin cancers can sometimes develop in:

• Scars from severe burns
• Areas of skin over serious bone infections
• Skin damaged by some severe inflammatory skin diseases

Psoralens and ultraviolet light (PUVA) treatments given to some people with psoriasis, a chronic inflammatory skin disease, can increase the risk of developing squamous cell skin cancer and probably other skin cancers.

Some medicines have been linked with an increased risk of squamous cell skin cancer. Examples include:

• Voriconazole
• Thiazide diuretics such as hydrochlorothiazide
• BRAF inhibitors such as vemurafenib, dabrafenib, and encorafenib
• Medicines that weaken your immune system (see below)

If you’re taking any of these medicines, talk to your doctor about your risk and whether there are things you can do to lower it.

This very rare inherited condition reduces the ability of skin cells to repair DNA damage caused by sun exposure. People with this disorder often develop many skin cancers, including SCC, starting in childhood.

Several other genetic syndromes have also been linked with an increased risk of squamous cell skin cancer. Examples include:

• Epidermolysis bullosa
• Fanconi anemia
• Muir-Torre syndrome
• Rothmund-Thomson syndrome
• Bloom syndrome
• Werner syndrome
• Oculocutaneous albinism

The immune system helps the body fight cancers of the skin and other organs. People with weakened immune systems from certain diseases or medical treatments are more likely to develop many types of skin cancer, including squamous cell carcinoma.

For example, people who get organ transplants are usually given medicines that weaken their immune system to help prevent their body from rejecting the new organ. This increases their risk of developing skin cancer. Skin cancers in people with weakened immune systems tend to grow faster and are often harder to treat.

People living with HIV, the virus that causes AIDS, often have weakened immune systems and also are at increased risk for squamous cell skin cancers.

Human papillomaviruses (HPVs) are a group of more than 200 viruses, many of which can cause papillomas, or warts. The warts that people commonly get on their hands and feet are not related to any form of cancer. But some HPV types, especially those that affect the genital and anal areas and the skin around the fingernails, are often related to squamous cell skin cancers in these areas.

People who smoke are more likely to develop squamous cell skin cancer, especially on the lips.

The most important way to lower your risk of squamous cell carcinoma and other skin cancers is to limit your exposure to UV rays. To learn more about UV exposure and what you can do to protect yourself and your loved ones, see How to Protect Yourself from UV Rays.

Look for shade

Simply staying in the shade is one of the best ways to limit your UV exposure.

Use sun protection

If you are going to be in the sun:

• Wear a shirt and a wide-brimmed hat.
• Apply sunscreen to areas not covered by clothing.
• Put on sunglasses to protect your eyes and sensitive skin around them.

Avoid tanning beds and sun lamps

Just like UV rays from the sun, the UV rays of tanning beds and sun lamps are harmful. Most skin doctors and health organizations recommend not using tanning beds and sun lamps.

Protect children from the sun

Children tend to spend more time outdoors and can burn easily, so they need special attention to protect their skin. Parents and other caregivers should protect children from excess sun exposure by keeping them in shady areas and making sure they wear sun protection. Children also need to be taught about the dangers of too much sun exposure as they become more independent.

Exposure to certain chemicals, such as arsenic, can increase a person’s risk of skin cancer. People can be exposed to arsenic from well water in some areas, pesticides, herbicides, some medicines, certain imported traditional herbal remedies, and certain occupations such as mining and smelting.

Checking your skin regularly might help you spot any new growths or abnormal areas before they have a chance to turn into skin cancer. If you find abnormal spots, it’s important to show them to your doctor to see whether they need to be treated. To learn more, see Early Detection, Diagnosis, and Staging of Squamous Cell Carcinoma of the Skin.

Smoking has been linked to an increased risk of squamous cell skin cancer, as well as to many other types of cancer. If you are thinking about quitting smoking and need help, call the American Cancer Society for information and support at 1-800-227-2345.

Infection with HIV, the virus that causes AIDS, can weaken your immune system and increase your risk for SCC and other cancers. Avoiding known risk factors for HIV infection, such as intravenous (IV) drug use and having unprotected sex with many partners, might lower your risk of skin cancer, as well as many other types of cancer.

Squamous cell cancers that start in the genital region account for a large proportion of the deaths from this type of skin cancer. Many of these cancers are related to infection with certain types of human papillomavirus (HPV), which can be spread through sexual contact. Limiting sexual partners and using safer sex practices such as wearing condoms might help lower the risk of some of these cancers.

Vaccines can also help protect against some types of HPV that can cause certain cancers. HPV vaccines are recommended in certain age groups to help lower the risk of some types of cancer, including squamous cell cancers in the genital area. To learn more, see HPV Vaccines.

Some people at increased risk for skin cancer, such as people with certain inherited conditions or a weakened immune system, might be helped by medicines that could lower their risk. This is known as chemoprevention.

Doctors are studying many drugs that might lower risk, although they are not commonly used at this time.

Nicotinamide, a form of vitamin B3, has been shown to lower the risk of BCCs and other skin cancers in people at high risk, and with very few side effects, although it hasn’t been studied extensively in people with weakened immune systems.

Vismodegib (Erivedge) is a targeted drug that has been shown to lower the number of new BCCs and to shrink existing tumors in people with basal cell nevus syndrome. This drug can have side effects, including taste loss and muscle cramps, which can make it hard for people to take it every day.