Squamous cell carcinoma is the second most common skin cancer, growing from the flat cells in the outer layer of your skin

Squamous cell carcinoma (SCC) starts in squamous cells — the thin, flat cells that make up most of your skin's outer layer. Unlike melanoma, which can spread quickly, squamous cell carcinoma usually grows slowly and stays in one place. When caught early, it responds well to treatment and rarely becomes life-threatening, though it can spread to other parts of your body if left untreated for years.

The cancer develops when sun damage or other injury causes these cells to grow abnormally. You may notice a firm, scaly bump, a sore that won't heal, or a rough patch of skin that bleeds easily. These spots most often appear on areas that get regular sun exposure — your face, ears, neck, hands, or scalp — but can form anywhere on your body.

Key Takeaways

  • Squamous cell carcinoma grows from flat cells in your skin's outer layer and usually develops slowly compared to other skin cancers.
  • The main cause is cumulative sun exposure over years, though it can also develop from old scars, burns, or chronic skin conditions.
  • Early signs include a firm, scaly bump; a sore that doesn't heal; or a rough, bleeding patch, most often on sun-exposed areas.
  • A skin biopsy is the only way to confirm squamous cell carcinoma; a dermatologist removes a small sample and sends it to a lab.
  • Treatment options include surgical removal, radiation, topical creams, or freezing, depending on the cancer's size, depth, and location.

How squamous cell carcinoma forms

Squamous cell carcinoma develops when UV radiation from the sun damages the DNA in squamous cells. Over time — usually years or decades — this damage accumulates and causes cells to grow in an uncontrolled way. The cancer almost always starts in the epidermis, the outermost layer of skin, and can remain there for a long time before growing deeper.

Sun exposure is the primary risk factor, but other things increase your chances. People with fair skin, a history of sunburns, or long-term outdoor work face higher risk. Squamous cell carcinoma can also develop in old burn scars, areas of chronic inflammation, or skin damaged by radiation therapy. Certain medications that suppress your immune system and conditions like psoriasis or lichen planus also raise your risk.

What squamous cell carcinoma looks and feels like

Squamous cell carcinoma takes different forms, so there is no single appearance. You might see a firm, dome-shaped bump with a scaly or crusted surface. Some look like a sore or ulcer that bleeds easily and doesn't heal within a few weeks. Others appear as a rough, thickened patch of skin, sometimes red or pink, sometimes the color of your skin or slightly darker.

The texture is often the key clue — the spot feels rough or scaly to the touch, different from normal skin. It may itch, bleed, or drain fluid. Most squamous cell carcinomas grow slowly, so you might notice the spot getting larger over weeks or months rather than days. Any skin growth that doesn't heal, bleeds repeatedly, or changes in size or appearance warrants a visit to a dermatologist.

Where squamous cell carcinoma typically appears

Squamous cell carcinoma develops most often on areas that receive the most sun: the face, ears, scalp, neck, and the back of the hands. It also commonly appears on the lips, especially the lower lip. People who work outdoors — farmers, construction workers, landscapers — develop it more frequently on exposed areas.

However, squamous cell carcinoma can form anywhere on your body, including areas that rarely see sun. It can develop on the genitals, inside the mouth, or on the soles of your feet. Location matters for treatment decisions: cancers on the face or ears may need different approaches than those on the trunk or limbs, because doctors balance removing the cancer with preserving appearance and function.

How doctors diagnose squamous cell carcinoma

A dermatologist cannot diagnose squamous cell carcinoma by looking at it alone. The only way to confirm it is with a skin biopsy. The doctor removes a small sample of the suspicious spot — usually under local anesthetic so you feel pressure but not pain — and sends it to a pathology lab. The pathologist examines the cells under a microscope and confirms whether it is squamous cell carcinoma, what type it is, and how deep it goes.

The biopsy results guide treatment decisions. The pathologist notes the cancer's grade (how abnormal the cells look), whether it has invaded deeper layers, and whether it shows high-risk features. This information helps your doctor predict how likely the cancer is to spread and what treatment will work best. If the biopsy shows squamous cell carcinoma, your doctor may order imaging or additional tests depending on the cancer's size and location.

Treatment options for squamous cell carcinoma

Treatment depends on the cancer's size, depth, location, and whether it shows high-risk features. For small, low-risk cancers, surgical excision — cutting out the cancer along with a margin of normal skin — is the most common approach. The procedure is usually done in an office setting under local anesthetic, and the wound is closed with stitches.

Other options include Mohs micrographic surgery, a technique where the surgeon removes the cancer layer by layer and checks each layer under a microscope to ensure all cancer cells are gone. This approach preserves the most healthy skin and is often used for cancers on the face or in sensitive areas. Cryotherapy (freezing with liquid nitrogen) works for very small, superficial cancers. Topical creams like imiquimod or 5-fluorouracil can treat cancers confined to the skin's surface. Radiation therapy is an option for people who cannot have surgery or whose cancer is in a difficult location.

Risk of recurrence and spread

Most squamous cell carcinomas do not return after treatment, but recurrence is possible — especially if the cancer was large, deep, or had high-risk features. Your doctor will tell you what to watch for and how often to have follow-up visits. Some people develop a second squamous cell carcinoma in a different spot years later, because the same sun damage that caused the first one can cause others.

Squamous cell carcinoma spreads to other parts of the body in a small percentage of cases, usually when the cancer has been present for years without treatment. When it does spread, it typically goes to nearby lymph nodes first, then to distant organs. High-risk features — large size, deep invasion, poor cell differentiation, or location on the ear or lip — increase the chance of spread. This is why early detection and treatment matter: catching squamous cell carcinoma when it is small and superficial makes serious complications unlikely.

Preventing squamous cell carcinoma

Since sun exposure is the main cause, sun protection is the most effective prevention. Use broad-spectrum sunscreen with SPF 30 or higher daily, even on cloudy days. Wear protective clothing — long sleeves, hats, and sunglasses — when you will be outside for extended periods. Avoid peak sun hours (10 a.m. to 4 p.m.) when UV radiation is strongest. Tanning beds and sun lamps also increase risk and should be avoided.

If you have a history of squamous cell carcinoma or precancerous spots called actinic keratosis, your dermatologist may recommend regular skin checks. Some people benefit from topical preventive treatments or oral medications that reduce the risk of new cancers. Protecting your skin now prevents not only squamous cell carcinoma but also melanoma and premature aging.

Frequently Asked Questions

Is squamous cell carcinoma life-threatening?

Most squamous cell carcinomas are not life-threatening, especially when caught early and treated. However, if left untreated for years, it can spread to lymph nodes and distant organs, which becomes serious. Early detection and treatment prevent this outcome in the vast majority of cases.

Can squamous cell carcinoma turn into melanoma?

No. Squamous cell carcinoma and melanoma are separate cancers that develop from different cell types. However, someone who develops one type of skin cancer has a higher risk of developing other types, because the underlying sun damage affects the entire skin.

What is the difference between squamous cell carcinoma and actinic keratosis?

Actinic keratosis is a precancerous spot — abnormal cells confined to the skin's surface that have not yet become cancer. Squamous cell carcinoma is cancer that has invaded deeper layers. Some actinic keratosis spots progress to squamous cell carcinoma if untreated, which is why dermatologists remove them.

Do I need chemotherapy for squamous cell carcinoma?

Most people do not. Surgery, radiation, or topical treatments cure the majority of squamous cell carcinomas. Chemotherapy is reserved for advanced cancers that have spread widely or cannot be treated with other methods, which is rare.

How often should I have my skin checked after treatment?

Your dermatologist will recommend a schedule based on your cancer's features and your risk factors. Many people have follow-up visits every three to six months for the first year or two, then annually. Ask your doctor what signs to watch for between visits and when to call if you notice something new.