Squamous cell carcinoma is the second most common type of skin cancer, developing when cells in the outer layer of skin begin to grow abnormally after damage from ultraviolet light. While most cases can be successfully treated when found early, understanding this condition and taking preventive steps can make all the difference in protecting your skin and overall health.
Understanding Squamous Cell Carcinoma
Squamous cell carcinoma, often abbreviated as SCC, starts in the squamous cells, which are flat cells that make up the middle and outer layers of your skin called the epidermis. These cells continuously shed and replace themselves as part of the skin’s natural renewal process. When these cells experience damage, particularly from the sun’s rays or other sources of ultraviolet radiation, they can begin to change and multiply in ways that are not normal. This abnormal growth leads to the formation of cancer.[1]
This type of skin cancer typically appears on parts of the body that receive the most sun exposure throughout a person’s lifetime. The face, ears, lips, neck, scalp (especially in people who are bald or have thinning hair), hands, arms, and legs are the most common locations. However, squamous cell carcinoma can develop anywhere on the body, including areas that are not regularly exposed to sunlight. In people with darker skin tones, the cancer is more likely to appear on areas that do not get much sun, such as the genital area.[1][3]
The appearance of squamous cell carcinoma can vary from person to person, which is why it’s important to be familiar with what might signal a problem. The cancer may show up as a rough, scaly patch of skin that can become crusty or bleed. It might look like a raised growth with a rough surface, or it could appear as an open sore that refuses to heal properly. Some people notice a growth that is higher than the surrounding skin but has a depression or dent in the middle. Other times, it presents as a flat area of red, scaly skin that measures roughly one inch or larger.[2][4]
Before squamous cell carcinoma fully develops, there are often early warning signs on the skin. These include rough, scaly patches known as actinic keratosis, which can feel dry and itchy. Another early sign is a lesion on the lower lip where the tissue becomes pale, dry, and cracked, sometimes with a burning sensation when exposed to sunlight. White or pale spots may appear in the mouth, on the tongue, gums, or inside of the cheeks, a condition called leukoplakia. These early changes may progress to cancer if left untreated.[2][4]
How Common Is Squamous Cell Carcinoma
Squamous cell carcinoma represents a significant and growing health concern around the world. In the United States alone, more than one million people receive a diagnosis of this condition each year. This makes it the second most frequently diagnosed form of skin cancer, trailing only basal cell carcinoma. What’s particularly striking is that the number of cases has been rising steadily over the past several decades.[2]
Over the last thirty years, the rate of squamous cell carcinoma diagnoses has climbed by approximately two hundred percent. This dramatic increase reflects both improved detection methods and changes in people’s sun exposure habits over time. The rise in cases has made this condition a major public health issue that requires attention from healthcare systems and communities alike.[2]
Certain groups of people face higher risks than others. Men are roughly twice as likely as women to develop squamous cell carcinoma. Age also plays a significant role, with people over the age of fifty being most commonly affected, although cases among younger individuals have been increasing. People over sixty-five years of age face particularly elevated risk. Those with fair or pale skin, blue or green eyes, and blonde or red hair are more vulnerable to developing this type of cancer. Geographic location matters too, with higher rates seen in areas that receive more intense sunlight throughout the year.[2][4]
What Causes Squamous Cell Carcinoma
At its core, squamous cell carcinoma develops because of changes, or mutations, in the genetic material of skin cells. The gene most commonly affected is called the p53 gene. This gene normally acts as a protector, controlling how cells grow, divide, and die. It functions as a tumor suppressor, meaning it helps prevent cancer by keeping cell growth in check. When the p53 gene becomes damaged or mutated, cells can begin to grow out of control, leading to cancer.[2]
The most common cause of these genetic mutations is exposure to ultraviolet (UV) radiation. This type of radiation comes primarily from the sun, but it also comes from artificial sources like indoor tanning beds and lamps. When UV rays penetrate the skin, they can damage the DNA inside skin cells. Over time, with repeated exposure, this damage accumulates. Eventually, the damaged cells may lose their ability to grow and function normally, setting the stage for cancer to develop.[1][2]
The damage from UV exposure is cumulative, meaning it builds up over a person’s entire lifetime. Someone who spent many hours in the sun as a child or young adult without proper protection may develop squamous cell carcinoma years or even decades later. This is why sun exposure at any age matters, and why protecting children’s skin is so important for their future health.[4]
While ultraviolet radiation is the primary culprit, other factors can also contribute to the development of squamous cell carcinoma. Exposure to certain chemicals, particularly arsenic and cigarette smoke, can increase risk. Chronic wounds or scars that don’t heal properly can sometimes become sites where cancer develops. Additionally, infections with certain types of human papillomavirus (HPV) have been linked to an increased likelihood of developing this cancer.[2][4]
Risk Factors for Developing Squamous Cell Carcinoma
Multiple factors can increase a person’s chances of developing squamous cell carcinoma. Understanding these risk factors helps people recognize when they need to be especially careful about skin protection and monitoring. One of the most significant risk factors is having a history of long-term sun exposure, particularly if that exposure occurred at a young age. People who work outdoors, such as construction workers, farmers, and lifeguards, face higher risk because of their daily exposure to the sun over many years.[2][4]
Physical characteristics related to skin and coloring also play an important role. People with fair or pale skin that burns easily are at greater risk than those with darker skin. Having blue, green, or gray eyes increases vulnerability, as does having blonde or red hair. These physical traits indicate less natural protection from melanin, the pigment that helps shield skin from UV damage.[2]
Age is another important factor. The risk of developing squamous cell carcinoma increases significantly after the age of fifty and continues to rise with advancing years. This reflects the cumulative nature of UV damage over time. Being sixty-five or older puts someone in a particularly high-risk category.[2]
A weakened immune system creates vulnerability to skin cancer. This includes people who have received organ transplants and must take medications that suppress their immune system to prevent rejection of the transplanted organ. People with conditions that naturally weaken immunity, such as HIV/AIDS or certain cancers affecting the immune system, also face elevated risk.[2][4]
Having certain skin conditions or previous skin problems increases risk as well. People with sunspots, also called solar keratoses or actinic keratoses, have a higher chance of developing squamous cell carcinoma. These rough, scaly patches represent areas where the skin has already been significantly damaged by the sun. Similarly, anyone who has had squamous cell carcinoma before faces a greater risk of developing it again, either in the same location or elsewhere on the body.[4]
Gender plays a role too, with males being approximately twice as likely as females to develop this type of skin cancer. The reasons for this difference may include differences in sun exposure patterns, occupational hazards, and possibly biological factors related to skin structure and response to UV damage.[2]
Recognizing the Symptoms of Squamous Cell Carcinoma
Being able to recognize the signs and symptoms of squamous cell carcinoma is crucial for early detection and successful treatment. The first symptom people often notice is a thick, rough, or scaly area on the skin that doesn’t seem to heal or go away on its own. This patch might feel different from the surrounding skin, with a texture that could be described as rough, crusty, or bumpy.[4]
The cancer may appear as a firm bump or lump that rises above the level of the surrounding skin. This growth might develop a crusty surface, similar to a scab, and it may bleed occasionally. Some people notice that the area bleeds easily when touched or rubbed, then scabs over, only to bleed again. This cycle of bleeding and scabbing that repeats itself is an important warning sign.[2]
Another common presentation is a sore or wound that simply refuses to heal. Unlike a normal cut or scrape that closes up and disappears within a week or two, a spot that might be squamous cell carcinoma will persist for weeks or months. Sometimes a sore appears to heal, giving false hope, only to open up again in the same location. This pattern of healing and recurring should prompt a visit to a healthcare provider.[2]
The appearance can also include raised growths that have an unusual feature: a depression or dent in the center. The edges might be elevated while the middle sinks down, creating a distinctive shape. Additionally, flat areas of red, scaly skin that measure an inch or more across can be a sign of this cancer.[2]
People may notice other sensations or symptoms in the affected area. The spot might itch, even persistently. It could feel dry despite moisturizing. The color might differ from the surrounding skin, appearing redder, pinker, or having other unusual coloring. Some growths take on a wart-like appearance, which can be misleading since warts are generally harmless.[2][3]
As squamous cell carcinoma grows into deeper layers of skin, it may begin to cause pain. What started as a painless spot can become tender or uncomfortable. This development of pain often indicates that the cancer is progressing and becoming more aggressive, making it even more urgent to seek medical attention.[4]
Prevention Strategies for Squamous Cell Carcinoma
Preventing squamous cell carcinoma largely centers on protecting your skin from ultraviolet radiation. Since UV exposure is the primary cause of this cancer, taking steps to minimize that exposure can significantly reduce your risk. These prevention strategies are important for everyone, but especially for those with known risk factors.[1]
The most fundamental prevention strategy is limiting direct sun exposure, particularly during peak hours. The sun’s rays are strongest between eleven in the morning and three in the afternoon. During these hours, UV radiation is most intense and most likely to cause skin damage. Whenever possible, staying in the shade during this time offers important protection. When you must be outside, seeking out shaded areas under trees, umbrellas, or covered structures helps minimize exposure.[4]
Protective clothing serves as a physical barrier between your skin and UV rays. Wearing long sleeves and long pants provides coverage for your arms and legs. Tightly woven fabrics offer better protection than loosely woven materials. Dark colors and denser fabrics block more UV radiation than light colors and thin fabrics. A wide-brimmed hat is essential for protecting the face, ears, and neck, all common sites for squamous cell carcinoma. The brim should be at least three inches wide all around to provide adequate shade.[4]
Sunglasses protect not only your eyes but also the delicate skin around them. Choose sunglasses that offer one hundred percent UV protection. Wraparound styles that cover the sides of your eyes provide the most complete protection. Labels should indicate protection against both UVA and UVB rays.[4]
Sunscreen is a critical tool in skin cancer prevention. Healthcare providers recommend using a sunscreen with a sun protection factor (SPF) of at least thirty. However, people who have had skin cancer previously may benefit from higher protection levels, such as SPF fifty. The SPF number indicates how well the sunscreen filters UVB radiation. But SPF alone isn’t enough; the sunscreen should also protect against UVA radiation. Look for products labeled “broad spectrum,” which protect against both types of UV rays. A star rating system on some products, with four or five stars being ideal, indicates strong UVA protection.[4]
Proper sunscreen application matters enormously. Many people don’t apply enough sunscreen to get the full protective benefit. It should be applied generously to all exposed skin, and it needs to be reapplied regularly throughout the day, especially after swimming, sweating, or toweling off. Sunscreen should be used even on cloudy days, since UV radiation can penetrate clouds and still damage skin.[4]
Avoiding indoor tanning is absolutely essential for prevention. Tanning beds and sunlamps emit UV radiation that damages skin just as the sun does, and they significantly increase the risk of developing squamous cell carcinoma and other skin cancers. There is no such thing as a safe tan from artificial UV sources.[1][2]
Regular skin self-examinations help with early detection, which improves treatment outcomes. Taking time every month or so to look carefully at your entire body helps you become familiar with what is normal for your skin. Look for any new spots, changes in existing moles or marks, or areas that look unusual. Check all areas, including those that don’t get much sun. Using a mirror or asking a family member to help can make it easier to see hard-to-view areas like your back, scalp, and the backs of your legs.[4]
Annual skin examinations by a healthcare provider, particularly a dermatologist, are important for people at higher risk. A trained professional can spot subtle changes that might be missed during self-examination. They can also monitor any concerning areas and recommend removal or biopsy when appropriate.[4]
How Squamous Cell Carcinoma Affects the Body
Understanding what happens inside the body when squamous cell carcinoma develops helps explain why this condition requires attention. At the cellular level, the disease begins when the DNA inside squamous cells becomes damaged. This damage most commonly occurs because of ultraviolet radiation breaking chemical bonds in the genetic material of cells. When these breaks happen repeatedly over time without proper repair, the instructions that tell cells how to grow and behave become corrupted.[2]
Normally, the p53 gene acts as a guardian of the cell. It monitors cell growth and can trigger cell death when it detects serious damage that cannot be repaired. This protective mechanism helps prevent damaged cells from multiplying and forming tumors. However, when UV radiation damages the p53 gene itself, this protective system breaks down. Without functional p53, damaged cells continue to divide and multiply even though they should stop or die.[2]
As abnormal squamous cells accumulate, they begin to form visible changes on the skin’s surface. At first, these changes might appear as rough, scaly patches. This early stage, where cancer cells exist only in the outermost layer of skin, is called in situ disease or Bowen’s disease. At this point, the cancer has not yet invaded deeper layers of skin. If detected and treated at this stage, the prognosis is excellent.[2][4]
If left untreated, the cancer cells may break through the thin membrane that separates the epidermis from deeper skin layers. When this happens, the cancer becomes invasive. It can grow downward into the dermis, the layer of skin beneath the epidermis that contains blood vessels, nerves, and other structures. As the tumor grows larger and deeper, it may cause pain and become more difficult to treat completely.[2]
In some cases, squamous cell carcinoma can spread beyond the original site. Cancer cells may break away from the primary tumor and travel through the lymphatic system, a network of vessels and nodes that normally helps fight infection and remove waste from tissues. These traveling cancer cells can lodge in nearby lymph nodes, causing them to swell. This spread to lymph nodes is called metastasis. While metastasis is relatively uncommon in squamous cell carcinoma compared to some other cancers, it can occur, especially when the original cancer is not treated promptly or when it appears in certain high-risk locations.[2]
The location and characteristics of the cancer affect how likely it is to spread. Squamous cell carcinomas on the lips, ears, and genitals are more prone to metastasis than those on other parts of the body. Larger tumors and those that have grown deep into the skin also carry higher risk of spreading. Tumors that develop in areas of previous injury, chronic inflammation, or radiation exposure tend to behave more aggressively.[6]
In rare but serious cases, squamous cell carcinoma can grow along tiny nerves in the skin. When this happens, cancer cells follow the path of these nerves, potentially reaching deeper structures. If a cancer on the face or scalp grows along nerves, there is a possibility it could eventually reach the brain, creating a very dangerous situation that requires intensive treatment.[6]
When squamous cell carcinoma does spread to distant parts of the body beyond nearby lymph nodes, it most commonly affects the lungs, liver, or bones. At this advanced stage, the disease becomes much more difficult to treat and can become life-threatening. This is why early detection and treatment are so important; catching the cancer before it has a chance to spread dramatically improves survival and quality of life.[2]
The body’s immune system plays an important role in recognizing and fighting cancer cells. A healthy immune system can often destroy abnormal cells before they develop into cancer. However, people with weakened immune systems, such as those who have received organ transplants or have certain chronic illnesses, have reduced ability to fight off developing cancers. This explains why immune suppression is such a significant risk factor for squamous cell carcinoma.[2]
