Squamous cell carcinoma (SCC) is the second most common form of skin cancer, second only to basal cell carcinoma. Millions of people are diagnosed with cutaneous SCC worldwide every year — around 1.8 million cases in the United States alone. Fortunately, SCC is curable in most cases when detected early.
In this article, we explain exactly what squamous cell carcinoma is, what it looks like, who is at risk, which tumours count as high-risk, and what treatment options are available.
What is squamous cell carcinoma (SCC)?
Squamous cell carcinoma (SCC) is a malignant tumour that develops from the squamous cells in the epidermis — the outermost layer of the skin. Squamous cells flatten out and form the protective outer layer of the skin, and when these cells mutate and grow uncontrollably, SCC develops.
Most squamous cell carcinomas grow slowly and stay where they started. Even so, around 2–5% spread to lymph nodes or other organs, and for high-risk tumours that figure rises to 10–30%. Spread is therefore not only something that happens if you wait too long — a high-risk tumour can metastasise despite correct treatment. What kind of lesion it is matters, not just how quickly it is treated.
What does squamous cell carcinoma look like?
SCC can appear in several forms:
- Red, scaly patch: A rough, thick or crusted area on the skin — often on sun-exposed areas such as the face, ears, neck or hands.
- Firm, wart-like bump: A firm bump with a reddish colour and rough, scaly surface.
- A sore that does not heal: An open sore that bleeds, oozes or forms a crust and does not heal despite treatment.
- Flat pink or red patch: With a slightly raised, rough edge and often a scaly surface.
SCC most commonly occurs on sun-exposed areas: face, ears, lips, neck, hands and forearms. However, it can appear anywhere on the body.
Why does squamous cell carcinoma occur?
The primary cause of SCC is chronic exposure to ultraviolet (UV) radiation from the sun or tanning beds. UV radiation damages the DNA in skin cells, and when this damage accumulates over time in the squamous cells, they can begin to grow uncontrollably.
What increases the risk of squamous cell carcinoma?
- Fair skin tone and light eyes: People with fair skin have less melanin protection against UV radiation.
- Chronic sun exposure: Prolonged time in the sun over many years significantly increases the risk.
- Sunburns: Especially severe sunburns in childhood and teenage years increase the risk.
- Tanning beds: Use of tanning beds before the age of 20 significantly increases the risk.
- Organ transplantation: Transplant recipients on lifelong immunosuppressive treatment have roughly 65–100 times the risk of SCC compared with the general population and should attend regular skin checks.
- Other forms of immunosuppression: People living with HIV have a much smaller increase — in the order of 2–5 times. Chronic lymphocytic leukaemia and long-term immunosuppressive medication also raise the risk.
- Precancerous lesions: Actinic keratoses (rough, scaly patches) are precursors to SCC and should be monitored.
Who gets squamous cell carcinoma?
SCC can affect anyone, but certain groups are significantly more vulnerable:
- People over 50 years old: The risk increases significantly with age, as UV damage accumulates over time.
- Men: Men generally have a higher incidence of SCC than women, partly due to differences in sun exposure and protective habits.
- People with fair skin: Especially people of Celtic or Northern European descent and those who burn easily.
- The immunocompromised: Organ transplant recipients and people with severe immunosuppression are at particular risk — both of developing SCC and of developing a more aggressive tumour.
Which squamous cell carcinomas are high-risk?
Most squamous cell carcinomas are cured by a single operation, but a minority behave aggressively and need specialist assessment quickly. A tumour is considered high-risk if it:
- sits on the lip or the ear
- is more than 2 cm across
- extends more than 6 mm deep
- is poorly differentiated under the microscope
- shows perineural invasion (growth along a nerve)
- has come back after previous treatment
- develops in someone who is immunosuppressed
If even one of these applies, ask for a prompt in-person dermatology assessment rather than waiting to see whether the lesion changes.
What can you do about squamous cell carcinoma?
SCC is highly treatable, especially when detected early. Several effective treatment options are available:
Surgical removal
The standard treatment for most SCC cases. Standard surgical excision or Mohs surgery (micrographic surgery, named after the surgeon Frederic Mohs) is used, especially on the face to preserve as much healthy skin as possible.
Radiation therapy
Used when surgery is not possible, or for high-risk SCC that cannot be adequately removed with surgery alone.
Topical medications
Creams such as 5-fluorouracil (5-FU) or imiquimod can be used for superficial SCC or actinic keratoses.
Photodynamic therapy (PDT)
A light-activated treatment that destroys cancer cells. Typically used for superficial SCC.
Medical classification: Squamous cell carcinoma is classified as 2C31 in the WHO's International Classification of Diseases (ICD-11). It is a skin cancer arising from squamous cells, often presenting as scaly, red patches. Surgical removal is the primary treatment.
How can you prevent squamous cell carcinoma?
Prevention is the best strategy against SCC. Here are the most important precautions:
- Use sunscreen year-round: Choose SPF 30 or higher and reapply every two hours during sun exposure.
- Avoid tanning beds: Tanning beds significantly increase the risk and should be avoided entirely.
- Protective clothing: Wear a hat, sunglasses and long-sleeved shirts during intense sun exposure.
- Avoid midday sun: Seek shade between 12:00 and 15:00, when UV radiation is strongest.
- Regular self-examination: Check your skin monthly for new or changing spots, especially if you are in a risk group.
- Actinic keratoses: Have actinic keratoses (rough, scaly patches) examined and treated before they develop into SCC.
Frequently asked questions
Is squamous cell carcinoma deadly?
SCC is rarely deadly when detected early. The five-year survival rate for localised SCC is above 95%. Around 2–5% of all cases spread, rising to 10–30% for high-risk tumours — spread can occur despite treatment and is not only a matter of having waited too long.
What is the difference between BCC and SCC?
Both BCC and SCC are skin cancers, but they develop from different cell types. Basal cell carcinoma develops from basal cells in the lower part of the epidermis, grows very slowly and almost never spreads. Squamous cell carcinoma develops from squamous cells in the epidermis and has a somewhat higher risk of spreading. Melanoma is the third main type and arises from the pigment cells.
When should I contact a dermatologist?
Contact a dermatologist if you notice a sore that does not heal within 4–6 weeks, a new or changing spot on the skin, or a rough, scaly patch that is growing or changing. Early diagnosis is crucial for successful treatment.
A photo assessment can tell you whether a lesion looks concerning enough to be seen in person, and how quickly. It cannot rule out skin cancer. A suspicious spot needs examination with a dermatoscope and, if there is any doubt, removal of the lesion for laboratory analysis.
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Disclaimer: This article is for informational purposes only and does not replace professional medical advice. Always consult a doctor or dermatologist for personal guidance and assessment of skin changes.