Causes and Risk Factors for Nonmelanoma Skin Cancer

Nonmelanoma skin cancer develops when skin cells sustain DNA damage that causes them to grow uncontrollably. Most cases are linked to ultraviolet (UV) radiation exposure from the sun or indoor tanning devices, although factors such as fair skin, advancing age, a weakened immune system and certain genetic conditions can also increase the risk.

Nonmelanoma skin cancer is the most common type of cancer in the United States. Basal cell carcinoma (BCC) is the most frequently diagnosed form, with an estimated 3.6 million cases diagnosed each year. Squamous cell carcinoma (SCC), the second most common form, accounts for approximately 1.8 million cases annually. Although most nonmelanoma skin cancers do not spread to distant parts of the body, early detection and treatment are important to prevent local tissue damage and other complications.

What causes nonmelanoma skin cancer?

Nonmelanoma skin cancer begins when genetic changes occur within skin cells, disrupting normal cell growth and repair processes. As these abnormal cells continue to multiply, they can form cancerous lesions on the skin’s surface.

In most cases, the DNA damage that leads to nonmelanoma skin cancer is caused by exposure to UV radiation. However, researchers believe that a combination of environmental, genetic and immune-related factors may contribute to its development.

Common causes associated with nonmelanoma skin cancer include:

• Ultraviolet (UV) radiation exposure – UV radiation from the sun and indoor tanning devices is the leading cause of nonmelanoma skin cancer. Repeated exposure can damage the DNA within skin cells, increasing the likelihood of cancerous changes.
• DNA mutations affecting cell growth – Genetic changes can interfere with the body’s ability to regulate cell division and repair damaged cells, allowing abnormal cells to multiply unchecked.
• Exposure to certain environmental carcinogens – Long-term exposure to harmful substances, such as arsenic, may increase the likelihood of skin cancer development.
• Immune system dysfunction – A weakened immune system may impair the body’s ability to identify and eliminate abnormal cells before they become cancerous.

What are the risk factors for nonmelanoma skin cancer? 

Although anyone can develop nonmelanoma skin cancer, certain characteristics, exposures and medical conditions can increase the likelihood of its development. Some risk factors are related to lifestyle choices, while others cannot be changed.

Check your skin regularly and get prompt attention if something is not right.

Vernon Sondak, MD

Chair, Cutaneous Oncology Program

Risk factors for nonmelanoma skin cancer include:

• Frequent sun exposure – Spending significant time outdoors without adequate sun protection can increase cumulative UV damage over time.
• History of sunburns – Severe or repeated sunburns can permanently damage skin cells and increase future skin cancer risk.
• Indoor tanning – Exposure to artificial UV radiation is strongly associated with both basal cell carcinoma and squamous cell carcinoma.
• Fair skin, light hair or light-colored eyes – Individuals with these traits generally have less melanin, which provides some natural protection against UV radiation.
• Increasing age – The risk of nonmelanoma skin cancer increases as UV-related skin damage accumulates over a lifetime.
• Weakened immune system – Organ transplant recipients and individuals taking immunosuppressive medications face a significantly higher risk of skin cancer.
• Personal history of skin cancer – Individuals who have previously been diagnosed with skin cancer are more likely to develop additional skin cancers.
• Exposure to radiation or arsenic – Prior radiation therapy or long-term arsenic exposure may increase the risk of certain skin cancers.
• Certain inherited conditions – Rare genetic disorders, such as xeroderma pigmentosum and basal cell nevus syndrome (Gorlin syndrome), can impair DNA repair mechanisms and increase susceptibility to skin cancer.

Which risk factors for nonmelanoma skin cancer are modifiable (factors you can control)?

Many nonmelanoma skin cancer risk factors are related to UV exposure and can be addressed through preventive measures. Taking steps to reduce UV damage and other avoidable exposures may help lower the likelihood of developing the condition.

Modifiable risk factors for nonmelanoma skin cancer include:

• Unprotected sun exposure – Limiting direct exposure to UV radiation and practicing sun safety can help reduce skin damage.
• Indoor tanning – Avoiding tanning beds and sunlamps can eliminate a significant source of artificial UV exposure.
• Inadequate sun protection – Failing to use sunscreen, protective clothing and other sun safety measures can increase skin cancer risk.
• Occupational and recreational UV exposure – Individuals who spend extended periods outdoors can lower their risk by consistently using sun protection and seeking shade when possible.
• Exposure to harmful environmental substances – Avoiding unnecessary exposure to carcinogens such as arsenic may help reduce skin cancer risk.

Which risk factors for nonmelanoma skin cancer are nonmodifiable (factors you cannot change)?

Some risk factors are beyond a person's control but may help identify individuals who could benefit from increased skin cancer awareness and monitoring.

Nonmodifiable risk factors for nonmelanoma skin cancer include:

• Age – The likelihood of developing nonmelanoma skin cancer generally increases with age.
• Fair skin, light hair or light-colored eyes – Individuals with these characteristics generally have less melanin and are more susceptible to UV-related skin damage.
• Personal history of skin cancer – Previous skin cancers increase the likelihood of developing future skin cancers.
• Family history of skin cancer – Inherited genetic traits may contribute to a higher risk.
• Inherited genetic disorders – Conditions such as xeroderma pigmentosum and basal cell nevus syndrome can significantly increase susceptibility to skin cancer.
• Immune system conditions – Some medical conditions that affect immune function may increase skin cancer risk and cannot always be prevented.

Can nonmelanoma skin cancer be prevented?

While not every case of nonmelanoma skin cancer can be prevented, many cases are linked to UV exposure and may be avoidable through consistent skin protection and awareness.

Strategies that may help reduce the risk of nonmelanoma skin cancer include:

• Use sunscreen daily – Apply a broad-spectrum sunscreen with an SPF of 30 or higher to exposed skin and reapply as directed.
• Seek shade when UV rays are strongest – Ultraviolet rays from the sun are typically strongest between 10 a.m. and 4 p.m. Seeking shade during these hours can help reduce exposure.
• Wear protective clothing – Long-sleeved shirts, long pants, wide-brimmed hats, sunglasses and UV-protective fabrics can help shield the skin from harmful UV radiation.
• Avoid indoor tanning – Eliminating exposure to tanning beds, booths and lamps can significantly reduce skin cancer risk.
• Perform routine skin self-examinations – Regularly checking the skin for new or changing lesions may help identify concerns early.
• Schedule professional skin examinations when appropriate – Individuals at increased risk for skin cancer may benefit from regular evaluations by a dermatologist or skin cancer specialist.

Frequently asked questions (FAQs) about nonmelanoma skin cancer causes and risk factors

Sun safety remains important year-round, even when temperatures drop and daylight hours become shorter. The following question addresses a common concern about skin cancer risk during the winter months:

• What are the risks of developing nonmelanoma skin cancer during the winter?

Find the help you need for nonmelanoma skin cancer at Moffitt Cancer Center

Most nonmelanoma skin cancers are linked to years of accumulated UV exposure, but early detection and treatment can help prevent more serious complications. Whether you are concerned about nonmelanoma skin cancer risk factors, a suspicious skin lesion or a recent diagnosis, Moffitt’s specialists can provide a comprehensive evaluation and individualized treatment recommendations.

If you would like to learn more about skin cancer, you can request an appointment with a specialist in the Cutaneous Oncology Program at Moffitt by calling 1-888-663-3488 or submitting a new patient registration form online. We do not require referrals.