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What triggers squamous cell carcinoma?


Squamous cell carcinoma (SCC) is one of the most common types of skin cancer. It arises from uncontrolled growth of abnormal squamous cells in the upper layers of the skin. SCCs often look like scaly red patches, open sores, elevated growths with a central depression, or warts. They may crust or bleed. SCC is mainly caused by cumulative ultraviolet (UV) exposure from the sun or tanning beds. People with fair skin, light hair and eye color have increased risk. However, anyone can get an SCC regardless of skin tone. Other potential causes or risk factors include radiation exposure, chronic inflammatory skin conditions, immune system suppression, chemical exposure, and certain strains of human papillomavirus (HPV). While highly curable in early stages, SCC can become disfiguring and life-threatening if allowed to grow.

What is Squamous Cell Carcinoma?

Squamous cells are flat cells found in the outer part of the epidermis, the top layer of the skin. These cells produce keratin, a protein that helps protect the skin from harm. Squamous cell carcinoma starts when DNA damage triggers some of these cells to multiply uncontrollably and form a mass of abnormal cells. As the abnormal cells outnumber normal cells, they invade deeper layers of the skin. At first, SCC may just look like a scaly red patch of skin. Over time, it can turn into an ulcer or wart-like growth. SCC has the potential to spread to other parts of the body, especially if left untreated.

Where Does Squamous Cell Carcinoma Develop?

SCC often occurs on sun-exposed areas of the body such as the face, ears, neck, lips, and backs of the hands. It can also develop in scars or chronic sores elsewhere. Areas that receive the most sun exposure over many years have increased risk. SCC sometimes arises in genital areas like the vulva, penis, anus, or inside the mouth, but this is less common.

Key Facts About Squamous Cell Carcinoma

  • SCC is the second most common type of skin cancer after basal cell carcinoma.
  • Around 700,000 cases are diagnosed each year in the United States.
  • It mainly affects fair-skinned middle-aged and elderly people.
  • Accumulated sun exposure is the biggest risk factor.
  • SCC may resemble a wart, red patch, ulcer, or sore that won’t heal.
  • Early treatment by surgical removal is highly effective.
  • Advanced SCC spreads in about 2-6% of cases.
  • Metastatic SCC has a poor prognosis with a disease-specific mortality of around 70% at 5 years.

Main Causes and Risk Factors

A number of factors can increase the likelihood of developing SCC. The most significant risks include:

UV Radiation

Too much ultraviolet (UV) radiation from sunlight or tanning beds is the #1 cause of SCC. UV exposure causes DNA damage that can lead to genetic mutations in skin cells. The more exposure over time, the higher the risk. People who work outdoors are particularly susceptible. Childhood sun exposure may be especially harmful. Using tanning beds before age 30 raises SCC risk by 75%. All skin types can develop SCC, but fair complexions have less melanin pigment to protect against UV damage.

Other Radiation Exposure

Ionizing radiation from X-rays, radiation therapy, or tanning booths can also damage skin cells and spur SCC growth later on. People treated for acne or hyperthyroidism with radiation have increased risk. SCCs may arise in old burn scars from radiation therapy.

Skin Injury

Chronic skin ulcers, wounds, burns, and inflammation can lead to SCC over time. Scars from severe acne or serious burns have a higher chance of becoming cancerous. Certain skin conditions like lupus, eczema, and xeroderma pigmentosum provoke inflammation that may trigger SCC development down the road.

Chemicals

Prolonged exposure to industrial chemicals like arsenic, coal, tar, and paraffin can inspire SCC formation decades later.

HPV

Human papillomavirus (HPV) is responsible for nearly all cervical cancers. But certain high-risk strains like HPV 16 also cause around 50% of SCCs in the genital region as well as 20% of SCCs in the head and neck area, especially the oropharynx. HPV is spread through sexual contact.

Immune Suppression

Anything that weakens the immune system makes you more susceptible to SCC. This includes HIV/AIDS, organ transplantation, chemotherapy, and immune-suppressing medications like TNF-alpha inhibitors used for autoimmune disorders.

Advanced Age

Most cases occur in people over 50. It’s thought that DNA repair mechanisms deteriorate with age, making skin cells more prone to UV damage. Fair elderly individuals have the highest rates of SCC. Still, due to high sun exposure, SCC can affect younger people as well.

Gender

Men are around twice as likely to develop SCC compared to women. This may be partially explained by more occupational sunlight exposure.

Skin Color

Light skin that tans poorly or freckles is more vulnerable to SCC. White populations have approximately 10 to over 200 times higher incidence rates than people with naturally darker skin. Albinos are at very high risk. Still, people of any race can get SCC on sun-exposed areas like the hands and face.

Blond/Red Hair; Blue/Green Eyes

Pale complexions with blond or red hair paired with blue or green eyes are more prone to UV skin damage and SCC development. However, darker complected individuals are certainly not immune.

Many Moles

Those with dysplastic nevus syndrome or more than 50 ordinary moles have a moderately increased risk of SCC. This may reflect underlying genetic susceptibility to skin cancer.

Personal History

If you’ve had SCC before, you’re at higher risk of getting another one. The more SCCs you’ve had, the greater the odds of recurrence. Around 35-50% of people develop additional lesions within 5 years. This may signal chronic sun damage or genetic predisposition.

Family History

Having a blood relative who’s had SCC raises your risk somewhat. Genetics that make skin more vulnerable to sun exposure may be a factor.

Smoking

Tobacco smoking modestly increases the likelihood of SCC, especially on the lips. The more you smoke and the longer you smoke, the higher the risk.

Alcohol

Drinking alcohol to excess may contribute slightly to SCC risk. This primarily applies to lips, tongue, mouth, throat and esophagus.

Prevention

Reducing exposure to SCC risk factors can lower your chances of developing this common type of skin cancer:

Limit Sun Exposure

To guard against UV damage, avoid prolonged time in midday sun, wear protective clothing and hats, and apply broad-spectrum, SPF 30 (or higher) sunscreen daily to exposed skin. Seek shade whenever possible. Sun protection should start in childhood.

Avoid Tanning Beds

Tanning devices concentrate UV radiation and significantly boost SCC risk. It’s best not to use them at all.

Protect Skin at Work

Outdoor workers should take extra precautions like wearing UV-blocking clothing, hats, and sunglasses, and repeatedly applying sunscreen to exposed body parts.

Watch for Suspicious Spots

Check your skin monthly for new lesions or changes in existing moles or spots. See a dermatologist promptly for evaluation of anything that seems abnormal. Early detection and treatment prevents progression.

Don’t Smoke

Avoid tobacco to eliminate its cancer-causing effects. If you currently smoke, quitting can still lower your risk compared to continuing smoking.

Limit Alcohol

Drink alcohol in moderation, if at all, to reduce associated SCC risks.

Practice Safe Sex

Using condoms decreases exposure to cancer-related HPV strains. Get vaccinated against HPV.

Get Cancer Screenings

Follow recommended screening guidelines for cancers like oral, skin, cervical, anal, etc. Finding cancer or precancer early is key. Discuss your level of risk and screening options with your doctor.

When to See a Doctor

Consult a dermatologist promptly if you notice any of the following on your skin:

  • A sore or bump that bleeds easily, crusts over, or doesn’t heal
  • A new growth or patch, especially on sun-exposed areas
  • A wart-like lesion that crusts or bleeds
  • A rough red patch with a raised border
  • A pink growth with central indentation
  • A rapidly changing mole or mark

Catching SCC early is key to effective treatment before it can spread. Make an appointment right away if you observe anything suspicious.

Diagnosis

To determine if a suspicious skin lesion may be SCC, the doctor will first examine it visually and may use a magnifying device to inspect it more closely. Further testing may include:

Biopsy

Removing all or part of the growth to examine under a microscope. A biopsy is the only definitive way to diagnose SCC. Types of biopsies used include:

  • Shave biopsy – Shaving off top layers of the lesion with a surgical blade.
  • Punch biopsy – Using a tool to remove a round, deep sample of tissue.
  • Excisional biopsy – Cutting out the entire growth.

Imaging Tests

For larger lesions or if cancer has spread to lymph nodes, imaging techniques such as CT, MRI, PET/CT, or ultrasound may be used to see if cancer has reached other organs.

Blood Tests

No blood test can confirm SCC, but certain blood tests can help evaluate if cancer may have spread to other body parts.

Staging

Once squamous cell carcinoma is diagnosed, further tests determine the stage or how far the cancer has progressed:

Stage 0

Cancer is only present in the epidermis, the outermost skin layer.

Stage 1

The tumor is 2 cm or less in size and has not spread deeper than the dermis, the skin’s inner layer.

Stage 2

The tumor is larger than 2 cm but has not spread to lymph nodes or other organs.

Stage 3

The cancer has invaded bones, muscles, nerves, ears, or eyes in the vicinity but not yet metastasized to distant sites.

Stage 4

The tumor has spread to lymph nodes or distant organs like the lungs, liver or brain.

Treatment

Several factors guide SCC treatment including the tumor’s stage, size, location, your age, and overall health. Common treatment options include:

Surgery

Surgical removal of the tumor is the standard first-line treatment for most SCCs:

  • Excision – Cutting out the tumor along with some normal surrounding skin.
  • Cryosurgery – Freezing and destroying abnormal cells with liquid nitrogen.
  • Curettage and Electrodesiccation – Scraping away cancer cells and then killing remaining ones with electric current.
  • Mohs surgery – Progressive surgical removal of skin layers while checking margins until no cancer cells remain. This preserves the most normal tissue possible.

Radiation Therapy

Using high-energy rays (or implanted radiation seeds) to kill cancer cells and shrink tumors. External beam radiation aims beams from a machine outside the body. It’s sometimes done after surgery if any cancer remains.

Chemotherapy Creams

Chemotherapy creams containing anti-cancer agents may be prescribed for some superficial skin lesions, especially in fragile elderly patients.

Photodynamic Therapy (PDT)

Applying a light-sensitive drug to the skin then activating it with a special light source to destroy cancer cells. Can be used for superficial SCCs.

Immunotherapy

Drugs prompting your immune system to better identify and destroy cancer cells. May benefit some people with advanced SCC.

Targeted Drug Therapy

Medications blocking specific molecules cancer cells need to grow. Some are approved for advanced SCC.

Prognosis and Survival Rates

With early diagnosis and proper treatment, most squamous cell carcinomas of the skin can be cured completely. The prognosis is excellent for Stage 1 and 2 lesions with no high-risk features. 5-year survival rates by stage are:

Stage 5-Year Survival Rate
Stage 0 Approximately 100%
Stage 1 More than 90%
Stage 2 70-90%
Stage 3 Around 50%
Stage 4 Roughly 25%

Factors associated with higher risk of recurrence and poorer outcomes include:

  • Larger tumor size
  • High-risk location like ear or lip
  • Rapid growth
  • Deep invasion into skin layers or structures
  • Poorly defined tumor borders
  • Recurrent lesions
  • Immune system suppression
  • Metastatic spread to lymph nodes or internal organs

Even when metastatic, treatments can often prolong life significantly. Discuss your particular prognosis with your oncologist.

Conclusion

In conclusion, accumulated UV light exposure, especially from the sun, is the predominant cause of squamous cell carcinoma of the skin. However, other factors like ionizing radiation, chronic skin damage or inflammation, chemical exposure, HPV infection, and immune suppression can also trigger SCC growth. Anyone can develop SCC, though fair individuals with a history of sunburns and tanning have substantially higher risk. Avoiding excessive sun, not smoking, and getting suspicious spots checked promptly are key prevention strategies. With early detection and proper treatment, SCC has a high cure rate. But metastatic SCC that invades deep or spreads to lymph nodes or organs becomes difficult to treat and can be fatal. Seeing a dermatologist right away about potential SCCs on your skin for prompt biopsy and treatment provides the best odds of survival.