Causes and Risk Factors for Squamous Cell Carcinoma

Key Takeaways

• Squamous cell carcinoma develops primarily due to DNA damage in squamous cells, most often triggered by prolonged ultraviolet (UV) radiation exposure.
• Chronic sun exposure and indoor tanning are among the most significant modifiable risk factors.
• Immunosuppression, human papillomavirus (HPV) infection, and exposure to certain chemicals substantially increase SCC risk.
• Fair-skinned individuals, older adults, and those with a history of skin conditions or prior skin cancers face an elevated risk.
• Early identification of risk factors enables proactive protective measures and regular dermatological screening.

Main Causes and Risk Factors for Squamous Cell Carcinoma

Squamous cell carcinoma develops when squamous cells accumulate genetic mutations that disrupt their normal growth cycle, causing them to multiply uncontrollably. These mutations most frequently result from external exposures that damage cellular DNA over time, though inherited genetic vulnerabilities can also play a role. According to the Skin Cancer Foundation, SCC accounts for approximately 1.8 million diagnoses annually in the United States alone, underscoring how widespread the disease has become.

The main causes of squamous cell carcinoma can be broadly grouped into environmental exposures, biological factors, and lifestyle-related behaviors. UV radiation remains the leading environmental driver, but a combination of factors often converges to create the conditions in which SCC can take hold. Recognizing this multifactorial nature is key to understanding why the disease affects certain individuals far more than others.

Chronic inflammation and persistent irritation of skin or mucosal tissue can also serve as a foundation for malignant transformation. Conditions such as chronic wounds, burn scars, or inflammatory skin disorders create an environment of sustained cellular stress, which may increase the likelihood of cancerous changes developing over decades of exposure.

UV Exposure and Its Role in Squamous Cell Carcinoma Risk

UV exposure and squamous cell carcinoma risk are closely and directly linked. Ultraviolet radiation — whether from natural sunlight or artificial sources such as tanning beds — penetrates the skin and causes characteristic DNA mutations in squamous cells, particularly in the tumor suppressor gene TP53. When these mutations accumulate without adequate DNA repair, the result can be the uncontrolled cell growth that defines SCC. The World Health Organization (WHO) classifies UV-emitting tanning devices as Group 1 carcinogens, the highest risk category, reinforcing the seriousness of artificial UV exposure.

Cumulative lifetime UV exposure is a more important measure of risk than any single instance of sunburn. People who spend extended periods outdoors for work or recreation — such as farmers, construction workers, and athletes — accumulate significant UV damage over years, making them particularly vulnerable. Even on overcast days, up to 80% of UV rays can penetrate cloud cover, according to the American Cancer Society, meaning that incidental daily exposure contributes meaningfully to long-term risk.

Actinic keratoses (AKs) are a well-recognized consequence of chronic UV exposure and are considered precancerous lesions. They present as rough, scaly patches on sun-damaged skin and, if left untreated, carry a meaningful risk of progressing to invasive SCC. Dermatologists recommend treating AKs promptly and monitoring sun-exposed areas regularly to reduce progression risk. Consistent use of broad-spectrum sunscreen, protective clothing, and shade-seeking behaviors are among the most effective strategies for limiting cumulative UV damage.

Who Is Most at Risk for Developing Squamous Cell Carcinoma

Several population groups carry a statistically higher likelihood of developing SCC based on a combination of biological, medical, and environmental factors. Recognizing these groups allows clinicians and individuals alike to prioritize targeted prevention strategies and more frequent dermatological surveillance.

People with fair skin, light hair, and light-colored eyes produce less melanin, the pigment that offers natural UV protection. As a result, their skin sustains more UV-induced DNA damage per unit of exposure compared with individuals who have darker skin tones. Older adults are also disproportionately affected, as the cumulative effects of UV radiation build over a lifetime; the incidence of SCC rises steadily after age 50, with men over 65 representing one of the highest-risk demographic groups.

Individuals who are immunocompromised face a substantially elevated risk. Organ transplant recipients, for instance, have a risk of developing SCC that is estimated to be 65 to 250 times higher than the general population, according to research published in clinical dermatology literature, due to the long-term immunosuppressive medications required to prevent organ rejection. People living with HIV/AIDS or those receiving immunosuppressive therapies for autoimmune diseases are similarly at increased risk, as their immune systems are less capable of identifying and eliminating abnormal cells before they progress.

The following groups are recognized as being at elevated risk for squamous cell carcinoma:

• Individuals with a personal or family history of skin cancer
• Organ transplant recipients on long-term immunosuppressive therapy
• People with inherited skin conditions such as xeroderma pigmentosum
• Those with a history of extensive or severe sunburns, particularly during childhood
• Workers with chronic occupational UV or chemical exposure
• Individuals with multiple or recurring actinic keratoses

Additional Triggers That Increase Squamous Cell Carcinoma Risk

Beyond UV radiation and immune status, several other squamous cell carcinoma causes and triggers are well-supported by clinical and epidemiological research. Human papillomavirus infection, particularly with high-risk HPV subtypes such as HPV-16 and HPV-18, is strongly associated with SCC of the oropharynx, genitals, and perianal region. The Centers for Disease Control and Prevention (CDC) estimates that HPV is responsible for approximately 70% of oropharyngeal cancers in the United States, a proportion that has increased significantly over recent decades.

Tobacco use — including cigarette smoking, pipe smoking, and smokeless tobacco — is a major independent risk factor for SCC of the head, neck, oral cavity, and esophagus. When combined with heavy alcohol consumption, the risk is compounded substantially, as alcohol may enhance the penetration of carcinogens into mucosal tissues and impair local immune defenses. This synergistic effect means that individuals who both smoke and drink heavily face a risk that is disproportionately greater than either factor alone would predict.

Occupational and environmental chemical exposures also contribute meaningfully to SCC development. Arsenic, which may be present in contaminated drinking water or certain industrial settings, is a recognized carcinogen linked to skin and internal SCC. Polycyclic aromatic hydrocarbons found in tar, soot, and certain lubricants have historically been associated with occupational skin cancers. Additionally, ionizing radiation — whether from therapeutic radiation treatment or other sources — can damage DNA in ways that predispose affected tissues to malignant transformation years or even decades after exposure.

Chronic inflammatory skin conditions, non-healing wounds, and long-standing burn scars represent another category of triggers. SCC arising within a chronic wound or scar is sometimes called Marjolin’s ulcer, a term used to describe malignant transformation in areas of persistent tissue damage. Although less common than UV-related SCC, these cases tend to be diagnosed at a more advanced stage because they may not be recognized as cancerous until significant progression has occurred.

Frequently Asked Questions

Can squamous cell carcinoma develop in people with darker skin tones?

Yes. While individuals with fair skin are at significantly higher risk due to lower melanin levels, squamous cell carcinoma can and does occur in people with darker skin tones. In these individuals, SCC more often develops in areas not typically associated with sun exposure, such as chronic wounds, scars, or mucous membranes. Because it is sometimes overlooked in darker-skinned patients, diagnosis may occur at a later stage, making awareness equally important across all skin tones.

Is squamous cell carcinoma hereditary?

A direct hereditary link to SCC is uncommon, but genetic factors can increase susceptibility. Inherited conditions such as xeroderma pigmentosum, which impairs the body’s ability to repair UV-induced DNA damage, carry a very high lifetime risk for multiple skin cancers including SCC. A personal or family history of skin cancer is also considered a risk factor. Genetic predisposition typically interacts with environmental exposures rather than acting as a standalone cause.

Does diet or nutrition influence squamous cell carcinoma risk?

Research on diet and SCC risk is still evolving. Some studies suggest that diets rich in antioxidants — found in fruits, vegetables, and whole grains — may support cellular repair mechanisms and reduce oxidative stress. Conversely, heavy alcohol consumption is an established risk factor, particularly for SCC of the head and neck. While no specific diet has been proven to prevent SCC, maintaining overall health through balanced nutrition may support the body’s natural defenses alongside proven preventive strategies such as sun protection.