Causes & Risk Factors Of Squamous Cell Carcinoma

September 10, 2023

Squamous cell carcinoma (SCC) is a form of skin cancer that grows in the middle and outermost layers of the skin. The cells in these layers are called squamous cells, and SSC is characterized by the uncontrolled growth of cells in this area. Squamous cell carcinoma is considered the second most common type of skin cancer and occurs more frequently in parts of the body and skin exposed to the sun, such as the face, arms, and legs.

Freckles and age spots are both indicators of sun damage that can lead to SCC. Symptoms of squamous cell carcinoma include red nodules, rough patches on the lips or inside the mouth, or wart-like sores that sometimes scab and bleed. Squamous cell carcinoma can become aggressive and cause severe complications if left untreated.

Ultraviolet Radiation


Spending too much time in the sun can increase an individual's risk of squamous cell carcinoma. The skin's exposure to ultraviolet radiation from sunlight causes cumulative sun damage over the years, which causes most cases of SCC. Individuals who spend long hours outdoors for work or leisure are risking the harmful effects of the sun's rays, such as golfers who spend many hours in the sun while enjoying the sport. Construction workers are also exposed to excessive amounts of radiation from the sun.

This makes the earlier claim clear that cancerous tumors most frequently appear on parts of the body exposed to the sun. Areas prone to squamous cell carcinoma include the face, arms, back, and hands. It can even develop on bald areas of the scalp, and the bottom lip and outer edge of the ear are especially at risk for developing this form of cancer. Individuals can lessen their risk of SCC by limiting time in direct sunlight, wearing sunblock, and covering their skin with clothing.

Fair Skin


Individuals of all skin tones are at risk for developing squamous cell carcinoma, though the cancer is much more common in those with fair skin, light-colored eyes, and red or blond hair. Individuals with very fair skin tend to burn easily and have a higher risk of developing the disease, and those who suffer from albinism are also at high risk for skin cancer because they produce a low rate of melanin.

Lighter-complected individuals have less melanin in their skin, and there's a greater likelihood of them developing SCC than those with darker skin. Melanin is a dark brown to black pigment that provides a protective effect against damaging UV radiation, and thus individuals with a tan or darker complexion have a lower risk of developing skin cancer compared to those with a fair to light complexion. However, studies show a shorter survival time for those who do develop it.

Use Of Tanning Beds

The use of tanning beds increases your risk of developing squamous cell carcinoma. Individuals who use them are two and a half times more likely to develop SCC than those who don't. The equipment used for indoor tanning produces and discharges UVA and UVB radiation. The amount produced may be even stronger than radiation from the sun in some cases. Research studies have shown exposure to ultraviolet radiation from tanning beds increases the risk of various cancers, including squamous cell carcinoma.

Researchers estimate the usage of tanning beds may cause almost half a million cases of skin cancer every year, and in fact, one tanning session can increase the risk of squamous cell carcinoma by sixty percent. Many experts believe their use is contributing to an increase in skin cancer cases among young women who use this method to darken their skin.

Xeroderma Pigmentosum

Xeroderma pigmentosum (XP) is a rare disorder that causes extreme sensitivity to ultraviolet radiation. The disorder decreases the body's ability to heal damage caused by radiation from the sun. Symptoms include flaky skin, pigmented spots, a serious sunburn after a short time in the sun, and other skin alterations. The risk of developing various forms of skin cancer, including squamous cell carcinoma, for patients with this disorder is almost one hundred percent if precautions are not taken.

Many XP patients are diagnosed with skin cancer from an early age because they are so prone to sun damage. Sufferers of the disorder burn and blister after a short time in the sun. Xeroderma pigmentosum patients can also experience eye problems, hearing loss, and neurological problems.

History Of Sunburns

Sun exposure in early life or a history of sunburns can increase an individual's risk of developing squamous cell carcinoma as an adult. Sunburns in adulthood are also a risk factor for SCC. A cancer study published in Cancer Epidemiology, Biomarkers & Prevention detailed the dangers of repeated occurrences of sunburn. The subjects were Caucasian women who experienced chronic sun exposure for hours at a time during their teen years.

Participants had at least five occurrences of severe sunburn from ages fifteen to twenty and had a sixty-eight percent increase in their risk for squamous cell carcinoma. The women exposed to the greatest cumulative amounts of ultraviolet radiation in their teen and adult years had a substantially increased risk for developing squamous cell carcinoma.

Actinic Keratosis

Actinic keratosis is a pre-cancerous scaly, rough patch on an individual's skin that forms after long-term exposure to the ultraviolet rays of the sun. Anyone who has actinic keratosis is at an increased risk of developing squamous cell carcinoma. Most affected individuals experience the appearance of an actinic keratosis after they reach forty years old because these skin patches take several years to form. The most common places on the body to find actinic keratosis is the face, ears, forearms, neck, lips, back of the hands, and scalp.

Some of these skin patches can be hard and wart-like. They can be a raised bump or flat on the top layer of the skin. These spots can be colored brown, pink, or red. One of these patches typically measures under an inch in diameter and may cause a burning or itching sensation in the affected region. Between two and ten percent of all actinic keratoses that go untreated will progress to squamous cell carcinoma. It is estimated between forty and sixty percent of all squamous cell carcinomas originated from actinic keratoses.

Bowen's Syndrome

Bowen's syndrome is a rare pre-cancerous condition of an individual's skin that causes the development of a gradually progressive plaque or red scaly patch on the skin. The cause of this syndrome is not clear, though extended sun exposure and age are known to play a significant role in its development. An individual affected by Bowden's syndrome is at a higher risk of developing squamous cell carcinoma. The skin lesions characteristic of Bowden's syndrome are red or brown, and they can be slightly raised or completely flat.

Some of these lesions may bleed, itch, crust over, ooze pus, and become tender. The lesions may fissure or split open, and they may also take on a verrucous or warty appearance. The lesion in Bowen's syndrome can develop anywhere on a patient's body, but the most common areas are on their legs, neck, head, and palms where the skin has been exposed to the ultraviolet rays of the sun. An estimated ten percent of all Bowen's syndrome patients will go on to develop squamous cell carcinoma.

Weakened Immune System


Individuals who have a weakened immune system for any reason are more likely to develop cancers of the skin, including squamous cell carcinoma. A number of mechanisms can cause an individual to have a weakened immune system. Individuals who have been the recipient of a donor organ have to take drugs that suppress their immune system to prevent organ rejection. Some individuals are affected by diseases that compromise their immune systems, like HIV and AIDS. Some individuals have a condition that requires the use of corticosteroid medications and other immune-suppressing drugs to stop their immune system from attacking healthy tissues.

The human immune system contains some cells with the ability to detect and flag cancer cells as abnormal so other immune cells can destroy them. While the immune system does not always eradicate all pre-cancerous cells on its own, it does aid in helping prevent the growth of malignancy in general. An individual who does not have a healthy immune system is more susceptible to developing not only squamous cell carcinoma but any type of cancer.

Long-Term Exposure To Chemicals

In some individuals, occupation-related long-term exposure to certain chemicals has caused them to develop squamous cell carcinoma. Certain chemicals can cause damage in the DNA of an individual's skin cells when it comes in contact with the skin. The longer someone is exposed to the substance, the greater the chance is for it to damage the portion of cellular DNA responsible for cell growth and division. When a mutation occurs in the growth and division part of the skin cell's DNA, malignancy is likely to develop. Certain occupations can cause an individual to be exposed to these substances while they are at the workplace.

Before it was discovered that certain substances could cause cancer, personal protective equipment was not a requirement. Individuals exposed to arsenic, mineral oils, herbicides, seed treatments, grease, dry cleaning agents, pitch, motor oil, or paraffin regularly can consequently develop squamous cell carcinoma. In addition, individuals exposed to coal tars, insecticides, fungicides, petroleum products, fiberglass dust, soot, creosote, and shale oils on a regular basis may also develop squamous cell carcinoma as a result.

Specific Eye Colors

Individuals who have specific eye colors are at higher risk of developing squamous cell carcinoma. The eye color, hair color, and skin tone of an individual are determined by how much melanin or pigment is present in their eyes, skin, and hair. Melanin is important because it is a defense mechanism used by the skin cells to deflect harmful ultraviolet rays away from healthy tissues. This mechanism is why an individual with no sun protection will form a tan in the sun.

Melanin becomes activated in the skin when it is exposed to the ultraviolet rays of the sun to protect the cells from damage. An individual with light skin has less overall melanin present in their body than those who have darker skin. Individuals with gray, green, or blue eyes are more likely to be fair skinned with a lighter hair color than individuals who have darker eyes. Because melanin offers protection to the skin cells, individuals with a lighter eye color who have less of it are at a higher risk of developing squamous cell carcinoma.

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