The Risks. The Causes. What You Can Do.
Squamous cell carcinoma (SCC) of the skin is caused by DNA damage that leads to abnormal changes (mutations) in the squamous cells in the outermost layer of skin.
Understanding what causes this damage and the factors that increase your risk of developing SCC can help you detect the disease early or prevent it from happening in the first place.
These factors increase your SCC risk:
- Unprotected exposure to ultraviolet (UV) radiation from the sun or tanning beds.
- Weakened immune system due to illness or certain immunosuppressive medications.
- History of skin cancer including basal cell carcinoma (BCC).
- Age over 50: Most SCCs appear in people over age 50.
- Fair skin: People with fair skin are at an increased risk for SCC.
- Gender: Men are more likely to develop SCC.
- Sun-sensitive conditions including xeroderma pigmentosum.
- Chronic infections and skin inflammation from burns, scars and other conditions.
- Skin precancers including actinic keratosis.
- History of human papilloma virus (HPV)
Unprotected exposure to UV radiation
Cumulative, unprotected exposure to UV radiation is the main cause of SCC as well as a risk factor for most skin cancers. The more time you spend in the sun over your lifetime — from long days at the beach to short periods of unprotected exposure — the greater your likelihood of developing SCC. If you work outdoors or spend extensive leisure or recreation time in the sun, your risk is especially increased.
It’s a fact: About 90 percent of nonmelanoma skin cancers are associated with exposure to UV radiation from the sun.
Your exposure to UV rays is also a risk that you can control. Find out more here.
It’s a fact
of nonmelanoma skin cancers are associated with exposure to UV radiation from the sun.
History of indoor tanning
Tanning beds emit UV radiation that is dangerous and raises your risk of developing SCC. People who have tanned indoors have a 67 percent increased risk of developing SCC compared with those who haven’t.
SCCs account for about 168,000 of the 419,000 cases of skin cancer diagnosed in the U.S. each year that are linked to indoor tanning.
In the last 30 years, the number of women under age 40 diagnosed with SCC has risen steadily — a statistic that experts also believe is linked to indoor tanning.
Weakened immune system
If your immune system is weakened or suppressed, you are more likely to develop SCC than people with healthy immune systems. This includes individuals with medical conditions that reduce immune function, including those with HIV, those receiving chemotherapy to treat cancer and those using immunosuppressive medications for autoimmune diseases. For organ transplant recipients on immunosuppressive antirejection drugs, the risk increases dramatically: Transplant patients are about 100 times more likely to develop SCC.
Excessive sun exposure also weakens the immune system, further raising the risk of developing SCC and other skin cancers in people with already compromised immune systems.
Skin cancer history
If you’ve had SCC, you have a high chance of recurrence. You also have an elevated risk of developing another SCC or basal cell carcinoma (BCC), since sun damage is the primary cause of both forms of skin cancer. If you have had a previous diagnosis of BCC, you also have a greater chance of developing SCC.
Age over 50
The risk of developing SCC increases as you age, and there is a reason why the disease most commonly occurs in people over 50. The longer you live, the more sun exposure and sun damage you accumulate. However, SCCs do occur in young adults, especially those who spend a lot of time in the sun and/or have used indoor tanning beds.
Although people of all skin types can develop SCC, people with fair skin — especially individuals with red or blond hair, blue or green eyes or skin that freckles or easily burns — have a heightened risk for the disease.
The threat of skin cancer still exists for people with darker skin tones, and the need for sun safety is absolutely essential. In fact, the majority of skin cancers in African Americans are SCCs, often arising in areas where previous skin conditions or inflammation has occurred. Recently, there has also been an uptick in new SCCs diagnosed in Latinos.
If you don’t know your skin type, take the quiz and find out.
Squamous cell carcinomas occur at least twice as frequently in men as in women. This is attributed to greater cumulative amounts of sun exposure in men.
People with xeroderma pigmentosum – a rare disorder that makes the skin less able to repair DNA damage caused by the sun – or other photosensitivity conditions such as polymorphous light eruption or solar urticaria have an elevated risk for skin damage, SCC and other skin cancers.
Certain precancerous growths, often resulting from cumulative sun damage, are linked with SCC.
Anywhere from 40 to 60 percent of all SCCs begin as an untreated precancerous lesion known as an actinic keratosis (AK). Anywhere from two to 10 percent of untreated AKs progress to SCC, sometimes as quickly as within two years, according to studies. Find out more about AKs here, and why you need to address them before they can become more serious.
This form of actinic keratosis occurs most often on the lower lip, causing it to become dry, cracked, scaly and pale or white. If not treated promptly, actinic cheilitis is at heightened risk of turning into an invasive squamous cell carcinoma.
Leukoplakias are white patches on the lips tongue, gums, cheeks or other places inside the mouth that can potentially develop into squamous cell carcinoma. They may be caused by sources of chronic irritation, such as regular alcohol consumption or tobacco use, or rough edges on teeth or dentures. Leukoplakias on the lips are mainly caused by sun damage.
Bowen’s disease (also known as squamous cell carcinoma in situ) is considered to be an early, noninvasive stage of SCC. It appears as a persistent red-brown, scaly patch that may resemble eczema. If untreated, it may penetrate more deeply, becoming a fully invasive SCC. Bowen’s disease on the skin is most often caused by exposure to the sun, but radiation, chemical carcinogens such as arsenic, genetics and trauma also may play a role.
Human papilloma virus (HPV)
HPV, which can arise in the mucous membranes of the nose and mouth as well as on the skin has been documented as a cause of Bowen’s disease on the genitals.
Elizabeth K. Hale, MD
C. William Hanke, MD
Last reviewed: February 2022