Squamous Cell Carcinoma: Symptoms, Causes & Treatment Options

What Is Squamous Cell Carcinoma?

Squamous cell carcinoma (SCC) is a cancer that develops in squamous cells, which are flat cells found in the upper layers of the skin (epidermis). It is the second most common form of skin cancer after basal cell carcinoma, with approximately 1.8 million cases diagnosed annually in the United States alone. SCC is primarily caused by cumulative UV radiation exposure from the sun or tanning beds.

Squamous cell carcinoma develops when squamous cells in your skin undergo DNA damage, typically from ultraviolet radiation. This damage accumulates over time, eventually causing the cells to grow and divide uncontrollably. Unlike some other cancers, SCC doesn't necessarily require you to have been severely sunburned—chronic, cumulative sun exposure is the main risk factor.

The disease primarily affects adults, with the risk increasing significantly after age 40 and continuing to rise with age. However, protecting children and young people from excessive sun exposure is crucial, as the UV damage that eventually leads to skin cancer begins accumulating early in life. Every sunburn in childhood or adolescence contributes to the lifetime risk of developing skin cancer.

Squamous cell carcinoma can develop anywhere on the body but most commonly appears on areas that receive the most sun exposure: the face, ears, neck, scalp (especially in bald individuals), backs of hands, and forearms. The cancer can also develop in scars, chronic wounds, or areas that have received radiation therapy in the past.

Understanding Skin Cell Layers

To understand SCC, it helps to know how your skin is structured. The epidermis, your skin's outermost layer, contains different types of cells. Squamous cells form the upper and middle layers of the epidermis. Below these are basal cells (where basal cell carcinoma originates), and scattered throughout are melanocytes (where melanoma originates).

When UV radiation damages the DNA in squamous cells, the cells may begin to grow abnormally. Initially, this may present as a precancerous condition called actinic keratosis. Over time, if left untreated, some actinic keratoses can progress to squamous cell carcinoma. This progression typically occurs gradually over months to years, which is why early detection and treatment of precancerous lesions is so important.

Types of Squamous Cell Carcinoma

There are several variants of cutaneous squamous cell carcinoma, each with slightly different characteristics:

• Squamous cell carcinoma in situ (Bowen's disease): This is an early, non-invasive form where abnormal cells are confined to the epidermis and have not invaded deeper tissues. It appears as a persistent, scaly red patch.
• Invasive squamous cell carcinoma: This form has penetrated beyond the epidermis into the dermis. It has the potential to spread to lymph nodes and distant organs if not treated.
• Keratoacanthoma: A rapidly growing dome-shaped tumor that may resolve on its own but is often treated as SCC due to difficulty distinguishing it from aggressive cancer.

What Are the Symptoms of Squamous Cell Carcinoma?

The most common symptom of squamous cell carcinoma is a rough, scaly patch or raised bump on sun-exposed skin, particularly the face, ears, neck, scalp, hands, or forearms. The lesion may be flesh-colored, pink, or red, and often has a crusted or ulcerated surface. Any skin change that persists, bleeds, or doesn't heal within 4-6 weeks should be evaluated by a dermatologist.

Recognizing the signs of squamous cell carcinoma early dramatically improves treatment outcomes. The appearance of SCC can vary considerably, which is why any persistent skin change warrants professional evaluation. The cancer typically develops in areas that have received significant sun exposure over your lifetime, though it can occur anywhere on the body.

Common characteristics of squamous cell carcinoma include:

• A firm, dome-shaped nodule or bump, often with a rough, scaly, or crusted surface
• A flat, reddish patch that may have an irregular border and scaly appearance
• A new sore or raised area on an existing scar, ulcer, or burn
• A rough, scaly patch on the lip that may evolve into an open sore
• A red, raised patch or wartlike sore inside the mouth
• A raised, crusted growth that may have a central depression
• A sore that bleeds easily, crusts over, and doesn't heal

Location Matters

The location of squamous cell carcinoma influences both its appearance and prognosis. Certain locations are associated with higher risk of aggressive behavior:

• Ear: SCC on the ear has a higher rate of metastasis and requires prompt treatment
• Lip: Particularly the lower lip, often appears as a persistent scaly patch or sore
• Scalp: Common in bald individuals; may appear as scaly, crusted areas
• Hands: Often develops on the backs of hands, may look like warts initially
• Areas of chronic inflammation: Can develop in long-standing ulcers, scars, or burns

Precancerous Warning Signs

Many squamous cell carcinomas develop from precancerous lesions called actinic keratoses (AKs). These are rough, scaly patches that feel like sandpaper on sun-damaged skin. While not all AKs progress to cancer, they serve as important warning signs that your skin has sustained significant UV damage. Treating AKs early can prevent progression to invasive cancer.

What Causes Squamous Cell Carcinoma?

The primary cause of squamous cell carcinoma is cumulative ultraviolet (UV) radiation exposure from sunlight or artificial sources like tanning beds. UV radiation damages the DNA in squamous cells, eventually leading to uncontrolled cell growth. Other risk factors include fair skin, immunosuppression, chronic wounds, exposure to certain chemicals, and previous radiation therapy.

Understanding what causes squamous cell carcinoma helps in both prevention and early detection. While UV radiation is the dominant risk factor, several other factors can contribute to the development of this cancer.

Ultraviolet Radiation

UV radiation is the most significant risk factor for developing SCC. Unlike melanoma, which is often linked to intermittent intense sun exposure and sunburns, SCC is more strongly associated with cumulative lifetime UV exposure. This means that years of everyday sun exposure—walking to your car, working in the garden, or spending time outdoors—contribute to your risk.

Both UVA and UVB rays contribute to skin cancer development, though they work differently. UVB rays are primarily responsible for sunburns and directly damage DNA in skin cells. UVA rays penetrate deeper into the skin and contribute to premature aging and cancer through indirect DNA damage and generation of harmful free radicals.

Indoor tanning is particularly dangerous. Using tanning beds before age 35 increases your risk of SCC by 67%. The World Health Organization classifies tanning beds as carcinogenic to humans, placing them in the same category as tobacco smoking and asbestos.

Other Risk Factors

While UV exposure is the primary cause, several other factors increase your risk of developing squamous cell carcinoma:

• Fair skin: People with Fitzpatrick skin types I and II (those who burn easily and tan minimally) have significantly higher risk due to less natural melanin protection.
• Age: Risk increases substantially after age 40 and continues rising with each decade.
• Immunosuppression: Organ transplant recipients taking immunosuppressive medications have 65-250 times higher risk than the general population. Other immunocompromised states also increase risk.
• Previous skin cancer: Having one SCC increases your risk of developing another. About 30-50% of people who have had one SCC will develop another within 5 years.
• Actinic keratoses: These precancerous lesions indicate high risk; about 10% may progress to SCC if untreated.
• Human papillomavirus (HPV): Certain HPV strains are associated with increased SCC risk, particularly in immunocompromised individuals.
• Chronic wounds: Long-standing ulcers, burns, or scars can develop SCC (Marjolin's ulcer).
• Chemical exposure: Arsenic and certain industrial chemicals increase risk.
• Previous radiation therapy: Areas that have received radiation treatment have increased risk.

How Is Squamous Cell Carcinoma Diagnosed?

Squamous cell carcinoma is diagnosed through a skin biopsy, where a sample of the suspicious tissue is examined under a microscope by a pathologist. Before biopsy, a dermatologist will perform a clinical examination, often using dermoscopy (magnified skin examination) to evaluate the lesion's characteristics. Additional tests may be needed if there's concern about spread to lymph nodes or other organs.

Accurate diagnosis is essential for determining the most appropriate treatment approach. The diagnostic process typically involves several steps, beginning with a thorough clinical examination.

Clinical Examination

During your appointment, the dermatologist will examine all skin lesions, not just the area of concern. You'll be asked about when you first noticed the lesion, whether it has changed in size or appearance, whether it bleeds or causes pain, and your history of sun exposure and previous skin cancers.

Dermoscopy, which uses a special magnifying instrument with polarized light, allows the dermatologist to see features not visible to the naked eye. This can help distinguish between SCC and other skin conditions, though a biopsy is usually needed for definitive diagnosis.

Skin Biopsy

A biopsy is the gold standard for diagnosing SCC. The procedure involves removing all or part of the suspicious lesion for microscopic examination. Types of biopsies include:

• Shave biopsy: A thin layer is shaved from the surface; used for superficial lesions
• Punch biopsy: A cylindrical sample is taken using a special tool; provides full-thickness specimen
• Excisional biopsy: The entire lesion plus a margin of normal tissue is removed; may be both diagnostic and therapeutic
• Incisional biopsy: Only part of a large lesion is removed for diagnosis

The biopsy specimen is sent to a pathology laboratory where a pathologist examines the cells under a microscope. The report will confirm whether cancer is present and provide important details about the tumor's characteristics, including depth of invasion and degree of differentiation (how abnormal the cells appear).

Lymph Node Examination

Because SCC can spread to lymph nodes, your doctor will examine nearby lymph nodes by palpation (feeling with hands). If any lymph nodes are enlarged or feel abnormal, a fine needle aspiration biopsy may be performed. This involves inserting a thin needle into the lymph node to collect cells for examination.

Imaging Studies

For most early-stage SCC, imaging is not required. However, if there's concern about spread beyond the skin, your doctor may order:

• CT scan: To check for spread to lymph nodes or other organs
• MRI: Particularly useful for evaluating perineural invasion (cancer spreading along nerves)
• PET scan: May be used in advanced cases to identify distant metastases

What Are the Stages of Squamous Cell Carcinoma?

Squamous cell carcinoma staging considers tumor size, depth of invasion, location, high-risk features, and whether the cancer has spread to lymph nodes or distant sites. Most SCCs are caught at an early stage and are highly curable. The AJCC staging system (stages 0-IV) is used, with higher stages indicating more advanced disease requiring more aggressive treatment.

Staging helps doctors determine the extent of the cancer and guides treatment decisions. For cutaneous SCC, staging considers multiple factors that affect prognosis.

High-Risk Features

Certain characteristics indicate a more aggressive tumor that may require more extensive treatment:

• Size: Tumors larger than 2 cm in diameter
• Depth: Invasion beyond 6 mm or into subcutaneous fat
• Location: Ear, lip, and sites of previous radiation therapy
• Differentiation: Poorly differentiated (very abnormal-appearing) cells
• Perineural invasion: Cancer spreading along nerve pathways
• Lymphovascular invasion: Cancer cells in blood vessels or lymphatic channels
• Immunosuppression: Patient has weakened immune system
• Recurrence: Cancer has returned after previous treatment

How Is Squamous Cell Carcinoma Treated?

Treatment for squamous cell carcinoma depends on the tumor's size, location, depth, and high-risk features. Surgical removal is the primary treatment for most cases, with options including standard excision, Mohs micrographic surgery, and curettage with electrodesiccation. Radiation therapy is an alternative when surgery isn't possible. Advanced or metastatic SCC may require immunotherapy with drugs like cemiplimab or pembrolizumab.

The goal of SCC treatment is complete removal or destruction of the cancer while preserving function and cosmetic appearance. The choice of treatment depends on multiple factors, and your dermatologist or oncologist will discuss the most appropriate options for your specific situation.

Treatment for Early-Stage SCC (Including Bowen's Disease)

Several effective treatments exist for early-stage squamous cell carcinoma and Bowen's disease (SCC in situ):

Cryotherapy (Freezing): Liquid nitrogen is sprayed on the lesion to destroy abnormal cells. This is most appropriate for small, superficial lesions and Bowen's disease. Local anesthesia may be used if scraping is required first. Healing typically takes 4-6 weeks, and some pigment changes may occur.

Curettage and Electrodesiccation (C&E): The tumor is scraped away (curettage) and the base is treated with electric current (electrodesiccation). This may be repeated 2-3 times. It's suitable for small, low-risk tumors but provides no tissue for margin evaluation.

Photodynamic Therapy (PDT): A photosensitizing medication is applied to the skin, then activated with a specific wavelength of light to destroy cancer cells. Treatment takes about 3 hours (medication application plus light treatment) and may need to be repeated. It works well for superficial tumors and Bowen's disease.

Topical Medications: For Bowen's disease and very superficial SCC, topical chemotherapy (5-fluorouracil) or immunomodulators (imiquimod) may be used. Treatment typically lasts several weeks with daily application.

Surgical Treatments

Standard Surgical Excision: The tumor is removed along with a margin of normal-appearing skin. The specimen is sent to pathology to confirm complete removal. This is appropriate for most low-risk SCCs. Margins are typically 4-6mm for low-risk tumors and larger for high-risk features.

Mohs Micrographic Surgery: The gold standard for high-risk SCC, especially on the face, ears, and other cosmetically or functionally sensitive areas. The surgeon removes thin layers of tissue and examines them under a microscope immediately, continuing until no cancer cells are seen at the margins. This technique offers the highest cure rates (up to 99%) while sparing the maximum amount of healthy tissue.

Mohs surgery is particularly recommended for:

• Tumors on the face, ears, lips, hands, feet, or genitals
• Large tumors or tumors with poorly defined borders
• Recurrent tumors
• Tumors with high-risk histological features
• Tumors in immunocompromised patients

Radiation Therapy

Radiation therapy uses high-energy beams to destroy cancer cells. It may be used when:

• Surgery isn't possible due to tumor location or patient factors
• After surgery when margins are positive or close
• For advanced SCC with lymph node involvement
• When perineural invasion is present

Treatment typically involves multiple sessions over several weeks. Side effects include skin irritation, redness, and potential long-term changes to the treated area.

Treatment for Advanced or Metastatic SCC

When squamous cell carcinoma has spread to lymph nodes or distant sites, more aggressive treatment is needed:

Lymph Node Surgery: If cancer has spread to lymph nodes, surgical removal of affected nodes (lymph node dissection) may be performed. This can lead to lymphedema in some cases.

Immunotherapy: Revolutionary treatments have transformed outcomes for advanced SCC. Immune checkpoint inhibitors help your immune system recognize and attack cancer cells:

• Cemiplimab (Libtayo): FDA-approved for locally advanced or metastatic SCC not curable by surgery or radiation
• Pembrolizumab (Keytruda): Also approved for advanced SCC

These medications are given by intravenous infusion, typically every 3 weeks. Response rates are approximately 40-50% for advanced SCC. Side effects can include fatigue, skin reactions, diarrhea, and immune-related adverse events affecting various organs.

Can Squamous Cell Carcinoma Come Back?

Yes, squamous cell carcinoma can recur at the original site (local recurrence) or develop as new tumors in other locations. About 30-50% of people who have had one SCC will develop another within 5 years. Local recurrence is more common in high-risk tumors and those treated with less definitive methods. Regular follow-up examinations are essential for early detection of recurrence.

Understanding the risk of recurrence helps you stay vigilant and maintain appropriate follow-up care. There are two distinct concepts to understand:

Recurrence: The original cancer returns, either at the same location (local recurrence) or in lymph nodes/distant sites (metastatic recurrence). This indicates that cancer cells remained after the initial treatment.

New primary tumor: A completely new SCC develops in a different location. This is not true recurrence but indicates that your skin has sustained sufficient UV damage to put you at ongoing risk.

Risk Factors for Recurrence

Certain factors increase the likelihood of recurrence:

• Incomplete removal with positive or close margins
• High-risk histological features
• Large tumor size (>2cm)
• Location on ear, lip, or areas of chronic inflammation
• Deep invasion or perineural invasion
• Immunosuppression
• Treatment with destruction methods (cryotherapy, C&E) rather than excision

Follow-Up Schedule

After treatment for SCC, regular follow-up is crucial. A typical schedule includes:

• Every 3-6 months for the first 2 years
• Every 6-12 months for years 3-5
• Annually thereafter

More frequent monitoring may be recommended for high-risk tumors or immunocompromised patients. During follow-up, your doctor will examine the treated area, check for new lesions, and palpate lymph nodes.

How Can You Prevent Squamous Cell Carcinoma?

Most squamous cell carcinomas can be prevented through consistent sun protection measures: using broad-spectrum SPF 30+ sunscreen daily, wearing protective clothing, seeking shade during peak UV hours (10 AM-4 PM), avoiding tanning beds, and performing regular skin self-examinations. For those with a history of SCC, treating precancerous actinic keratoses is also important.

Prevention is the most effective strategy against squamous cell carcinoma. Since UV exposure is the primary cause, protecting your skin from UV radiation throughout life significantly reduces your risk.

Sun Protection Strategies

Sunscreen: Apply broad-spectrum (UVA/UVB) sunscreen with SPF 30 or higher to all exposed skin daily, even on cloudy days. Reapply every 2 hours and immediately after swimming or sweating. Use approximately one ounce (a shot glass full) to cover your entire body.

Protective Clothing: Wear tightly woven, loose-fitting clothing that covers your arms and legs. Dark colors and denser fabrics provide more protection. Consider UPF-rated clothing designed for sun protection.

Hats: Wear a wide-brimmed hat (3 inches or more) that shades your face, ears, and neck. Baseball caps leave the ears and neck exposed.

Sunglasses: Wear UV-blocking sunglasses to protect your eyes and the delicate skin around them.

Seek Shade: When possible, stay in the shade during peak UV hours (typically 10 AM to 4 PM). Remember that UV rays can reflect off water, sand, and snow.

Avoid Tanning Beds: There is no safe way to use a tanning bed. Even one indoor tanning session increases your skin cancer risk.

Regular Skin Examinations

Early detection saves lives. Perform monthly self-examinations of your entire body, using mirrors to check hard-to-see areas. Look for any new growths, changes in existing spots, or sores that don't heal. Document your findings with photos to track changes over time.

Schedule annual professional skin examinations with a dermatologist. Those with a history of skin cancer or multiple risk factors should have more frequent examinations as recommended by their doctor.

Treating Precancerous Lesions

Actinic keratoses (AKs) are precancerous lesions that can progress to SCC. Treatment options include:

• Cryotherapy (freezing)
• Topical medications (5-fluorouracil, imiquimod, diclofenac)
• Photodynamic therapy
• Chemical peels
• Laser treatment

How Does Squamous Cell Carcinoma Affect Daily Life?

For most people treated for squamous cell carcinoma, there are no permanent physical limitations after treatment, and they can return to normal activities. However, the experience can have lasting emotional impact, and ongoing vigilance with sun protection and skin monitoring becomes a permanent part of life. Some may experience anxiety about recurrence, which is normal and can be addressed with appropriate support.

Being diagnosed with skin cancer, even a highly treatable form like early-stage SCC, can be emotionally challenging. Understanding what to expect can help you navigate this experience.

Emotional Impact

It's normal to experience a range of emotions after a cancer diagnosis, including anxiety, fear, anger, or sadness. Many people worry about recurrence, even when their prognosis is excellent. These feelings typically improve over time, but if they persist or interfere with your daily life, consider speaking with a mental health professional who has experience with cancer patients.

Lifestyle Adjustments

After treatment for SCC, you'll need to make sun protection a priority for the rest of your life. This doesn't mean avoiding the outdoors—rather, it means being smart about when and how you spend time in the sun. Many people find that these habits become second nature over time.

You may also become more aware of your skin, which is actually beneficial for early detection of any new problems. Monthly self-examinations and regular dermatologist visits become part of your routine.

Treatment Follow-Up

Follow-up schedules vary based on your tumor's characteristics and your individual risk factors. Your dermatologist will recommend an appropriate monitoring plan. It's important to keep all follow-up appointments and to contact your doctor promptly if you notice any concerning changes.

Getting Support

Various resources are available to help you cope with a skin cancer diagnosis:

• Skin cancer support groups (in-person or online)
• Cancer counselors or psychologists
• Patient advocacy organizations
• Friends and family
• Your healthcare team