Skin cancer types: Squamous cell carcinoma causes
What causes squamous cell carcinoma?
The cause of most squamous cell carcinoma (SCC) of the skin is well known. People usually develop this skin cancer because ultraviolet (UV) light has badly damaged their skin. Most UV light comes from:
Indoor tanning equipment (such as tanning beds and sunlamps)
Sun exposure without sun protection
Spending time in the sun without protecting your skin from the sun greatly increases your risk of developing squamous cell carcinoma of the skin.
How can UV light cause skin cancer?
Every time UV light hits our skin, it can damage some of the DNA inside our skin’s cells. This happens every time we:
Spend time in the sun without sun protection
Use indoor tanning equipment
The body tries to repair this damage. When the body can no longer repair all the damage, changes called mutations develop in our skin’s cells. The mutated cells, which are cancer cells, can multiple quickly. As these cells pile up, a tumor develops.
When a tumor forms in skin cells called squamous cells, we get SCC of the skin. These cells are found in the outermost layer of our skin, which is called the epidermis. The following picture shows you where these cells live.
Do some people have a higher risk of developing squamous cell carcinoma skin cancer?
Yes. The key risk factors for getting this skin cancer are listed below. A risk factor is anything that increases your risk of developing a disease.
UV-damaged skin caused by the sun or tanning beds. While most people get this skin cancer because the sun’s UV rays damaged their skin, tanning also increase the risk. Using a tanning bed once can increase your risk of developing SCC of the skin by 67%1.
Fair skin, light-colored eyes, or naturally red or blond hair. If you have any of these traits, your skin is more easily damaged by the sun.
Sunburns. If you’ve had blistering sunburns, especially in your youth, you have a higher risk of developing SCC of the skin.
Actinic keratoses (AKs). These are precancerous growths on your skin, which are caused by the sun or indoor tanning. Having an AK increases your risk of developing SCC because an AK can progress and turn into SCC of the skin. While not every AK turns into skin cancer, dermatologists recommend treating AKs to prevent this.
Sunny region. Living in an area that’s warm and gets plenty of sun year-round, such as Florida or California, increases your risk.
High altitude. Living at a high altitude also increases your risk.
Previous skin cancer. Having had skin cancer increases your risk of developing more skin cancers.
Organ-transplant recipient. If you have a transplanted organ, such as a kidney, heart, or lung, you have a significantly increased risk of developing SCC of the skin. Being under a dermatologist’s care can help you manage this increased risk.
HPV infection. This skin cancer can develop under a nail, on the genitals, or inside the anus. Researchers have found that in these areas, the cancer is often accompanied by an HPV (human papillomavirus) infection.
Skin injury, such as a burn. Have you burned your skin badly? If so, you have a higher risk of developing skin cancer on the skin that was burned. Skin cancer can develop in scar tissue that forms after a serious burn or other injury. SCC of the skin is the most common skin cancer that forms where skin has been badly burned. The cancer tends to appear years after the injury.
A serious injury to a fingernail or toenail may lead to developing this skin cancer under a nail.
Exposure to arsenic. People who have levels of arsenic in their drinking water or food have a higher risk of developing SCC of the skin. As many pesticides contain arsenic, people who spend a lot of time around pesticides also have an increased risk.
Cigarette smoking. Some studies suggest that smokers develop this skin cancer at an earlier age than do people who don’t smoke or have never smoked.
HIV. In looking at medical records, Danish researchers found that people who are HIV positive have a higher risk of developing the most common types of skin cancer, including SCC of the skin. In this study, the risk of developing SCC was 5.40% higher in people who were HIV positive than in people who did not have HIV.2
Weakened immune system. Our immune system helps defend against cancer, so when something weakens it, we have a greater risk of developing skin cancer. Some medications, such as those that help prevent the body from rejecting a transplanted organ, weaken the immune system. Diseases such as leukemia, also weaken the immune system.
Xeroderma pigmentosum or similar inherited disease. Some people are born with a medical condition called xeroderma pigmentosum (XP). If you have XP, your body cannot repair any of the damage caused by UV light, so your risk of developing skin cancer skyrockets. It’s estimated that XP can raise the risk of getting skin cancer 10,000-fold.
While having one or more risk factors for SCC of the skin increases your risk of developing it, some people who get this skin cancer don’t seem to have any risk factors. People of all colors get this skin cancer, including people of African, Asian, and Latin descent.
If you find a spot on the skin that is growing, bleeding, or changing in any way, see a board-certified dermatologist to find out what it is. You’ll find out how this skin cancer is diagnosed and treated at, Squamous cell carcinoma of the skin: Diagnosis and treatment.
1 American Academy of Dermatology. Indoor tanning fact sheet. Last accessed January 31, 2019.
2 Omland SH, Ahlstrom MG, et al. “Risk of skin cancer in patients with HIV: A Danish nationwide cohort study.” J Am Acad Dermatol 2018;79:689-95.
Anadolu-Brasie R, Patel AR, et al., “Squamous cell carcinoma of the skin.” In: Nouri K, et al. Skin Cancer. McGraw Hill Medical, China, 2008: 86-114.
Nadhan KS, Chung CL, et al. “Risk factors for keratinocyte carcinoma skin cancer in nonwhite individuals: A retrospectiveaAnalysis.” J Am Acad Dermatol (2019), doi: https://doi.org/10.1016/j.jaad.2019.01.038.
Haley CT, Mui UN, et al. “Human oncoviruses: Mucocutaneous manifestations, pathogenesis, therapeutics, and prevention (Part I: Papillomaviruses and Merkel cell polyomavirus).” J Am Acad Dermatol (2018), doi: https:// doi.org/10.1016/j.jaad.2018.09.062.
Omland SH, Ahlstrom MG, et al. “Risk of skin cancer in patients with HIV: A Danish nationwide cohort study.” J Am Acad Dermatol 2018;79:689-95.
Que SKT, Zwald F, et al. “Cutaneous squamous cell carcinoma Incidence, risk factors, diagnosis, and staging.” J Am Acad Dermatol 2018;78:237-47.