Squamous cell carcinoma is a common type of skin cancer caused by an overgrowth of squamous cells in your epidermis, the top layer of your skin. In the U.S., it’s the second most frequently diagnosed skin cancer, right after basal cell carcinoma, with an estimated 1.8 million cases diagnosed each year.
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What Is Squamous Cell Carcinoma?
Squamous cell carcinoma (SCC) is a common type of cancer that starts in squamous cells, which are thin, flat cells found in many parts of the body. These cells line the passageways and hollow organs in the body, including the nasal passageways, mouth, throat, esophagus, lungs, and cervix.
When SCC develops in the skin, it’s often referred to as squamous cell skin cancer (SCSC) or cutaneous squamous cell carcinoma. This cancer arises from squamous cells that compose most of the epidermis, the outer layer of the skin. These cells are regularly shed and replaced as part of the skin’s natural cycle.
When squamous cells begin to grow uncontrollably, they can turn into cancer. SCSC tends to develop after years of ultraviolet (UV) light exposure. It grows slowly and is most often found on parts of the body that get a lot of sun, like the ears, scalp, and backs of the hands. It may appear as a sore that won’t heal or as a red, scaly patch that keeps getting larger.
Although it’s a relatively slow-growing malignant (cancerous) tumor, it can metastasize (spread) to surrounding tissues if left untreated. Squamous cell carcinoma may even spread to the sinuses, skull base, or other areas of the brain.
What are the stages of squamous cell carcinoma of the skin?
There are five stages of skin cancer:
- Stage 0 (in situ) — Cancer cells are localized in the uppermost layer of the skin.
- Stage 1 — Cancerous area is less than 2cm and has not spread.
- Stage 2 — Cancerous area is larger than 2cm and may have spread to nearby tissue but not to lymph nodes.
- Stage 3 — Cancerous area of any size that has spread to lymph nodes.
- Stage 4 — Cancerous area has become invasive, spreading to other body parts.
How common is squamous cell carcinoma?
Squamous cell carcinoma is the second most common skin cancer in the United States, behind basal cell carcinoma.
Approximately 1 million cases of squamous cell skin cancer are diagnosed in the United States each year. But that number is probably an underestimate because non-melanoma skin cancers are not tracked by health officials. The actual number is likely higher.
About 7,000 people die from squamous cell skin cancer each year in the United States. In the southern and central parts of the United States, SCSC is more prevalent due to increased sun exposure. In these regions, the SCSC death rate approximates that of kidney cancer, head-and-neck cancer, and melanoma.
What causes squamous cell carcinoma?
Squamous cell carcinoma (SCC) develops when squamous cells — flat cells found on the surface of the skin and in various internal linings — start to grow abnormally and spread beyond their original layer.
Squamous cell carcinoma risk factors
The risk factors for SCSC are:
- Being exposed to certain toxic chemicals – Including arsenic, and carcinogens in tar, pitch, soot, etc.
- Being immunocompromised – At-risk groups include people who have had organ transplants, HIV, and certain blood cancers.
- Being male – Men are three times more likely than women to develop squamous cell skin
- Being older – The average age when people develop SCSC is 65.
- Having certain genetic mutations – Including albinism (lack of color in hair, skin, or eyes) and xeroderma pigmentosum (XP), a squamous cell carcinoma in which the body can’t repair damage to DNA caused by the sun.
- Having fair (light) skin – Whilelight skin is at higher risk, it doesn’t mean people of color can’t develop squamous cell skin cancer. They can.
- Having had an organ transplant – Organ transplant recipients are 65 to 250 times more likely to develop SCSC than the general population, depending on the type of organ transplant and the immunosuppression regimen.
- Having HIV/AIDS.
- Having human papillomavirus (HPV).
- History of actinic keratoses (scaly spots on sun-damaged skin) or previous skin cancers.
- History of cumulative unprotected exposure to sunlight or other UV radiation – UV exposure during childhood and adolescence is a bigger risk factor than exposure during adulthood. Nevertheless, people who work outdoors or spend a lot of their leisure time outside are at high risk.
- Smoking – Self-explanatory.
Complications of squamous cell carcinoma
Complications of cutaneous squamous cell carcinoma include:
- Local invasion.
- Loss of function.
- Metastases.
- Pain.
- Poor cosmetic appearance after removal.
Death can also result from untreated SCSC.
What Are the Signs and Symptoms of Squamous Cell Carcinoma?
Possible signs of this skin cancer include:
- Brown spot that looks like an age mark.
- Firm, dome-shaped bump.
- Open sore with a raised edge.
- Rough, red, scaly patch.
- Sore that develops in an old scar.
- Tiny, horn-like projection from the skin.
- Wart-like growth.
Where it tends to appear:
- Areas frequently exposed to the sun – Face, lips, bald scalp, ears, and hands.
- Skin that’s been heavily damaged by sun exposure or indoor tanning
Signs of sun-damaged skin:
- Age spots.
- Deep wrinkles.
- Loss of skin firmness.
- Uneven or discolored skin tone.
When should I see a doctor about my squamous cell carcinoma symptoms?
Contact your health care provider if you have any squamous cell carcinoma symptoms.
Although skin cancer often grows slowly over years rather than months, treatment should not be delayed. Ignoring SCSC can give it time to become invasive squamous cell carcinoma, which may spread to nearby lymph nodes and organs, including the brain and bones.
When caught early, most SCSCs are highly treatable, but survival decreases the longer the disease is left untreated.
How Do You Diagnose Squamous Cell Carcinoma?
Squamous cell carcinoma of the skin can be diagnosed by:
- Medical history — Including your sun exposure and general health background.
- Skin exam — Including identification of precancerous lesions, such as actinic keratoses.
Squamous cell carcinoma of the sinuses, skull base, or brain can be diagnosed by:
- Imaging studies — Such as MRI or CT scans, to identify the presence and exact location of the tumor.
Tests to diagnose squamous cell carcinoma
- Biopsy of suspicious areas — Quick and done in the office.
During your visit, your doctor may numb the area and take a small sample of tissue, called a biopsy. The removed tissue sample will be sent to a laboratory and examined under a microscope by a pathologist or dermatopathologist, a specialist trained in analyzing skin tissue. After reviewing the sample, the pathologist prepares a report describing what was found under the microscope and sends it to your doctor.
This report will include whether any signs of cancer are present. If squamous cell carcinoma is diagnosed, the report may also include:
- The specific type of squamous cell skin cancer.
- Whether the cancer shows any features to suggest it may behave aggressively.
How Do You Treat Squamous Cell Carcinoma?
Squamous cell carcinoma treatment varies based on the location and size of the tumor. A combination of surgical and nonsurgical approaches may be recommended to treat squamous cell carcinomas.
Options include:
Chemotherapy
Chemotherapy treatment uses drugs to stop the growth of cancer cells. Depending on the type and stage of the cancer, chemotherapy may be taken by mouth, injected, or placed directly into the tumor site.
Radiation therapy
Radiation is commonly used to treat tumors in hard-to-reach areas where surgery isn't always an option.
Radiation therapy may be delivered:
- Externally by directing radiation at the tumor from an outside source.
- Internally by placing radioactive material directly in the body near the cancer.
- Using image-guided stereotactic radiotherapy (SRT) to deliver multiple low doses of x-ray energy to target cancer from the surface down.
- Using stereotactic radiosurgery (SRS) to deliver one concentrated dose of radiation directly to the tumor.
Surgery
Curettage and electrodesiccation
In this type of surgical removal, the doctor first scrapes the tumor from your skin using the curetting technique. Next, the doctor applies an electrode to the site of the tumor to destroy any remaining cancer cells.
Dermatologists may choose this method to treat small squamous cell skin cancers that are considered low-risk. However, it's typically not used for cancers located on the head or neck, or in areas with dense hair growth — like the calp, beard region, or armpits.
Excision
Excision is the surgical removal of an abnormal lesion, tissue, or tumor from the body, often along with a margin of healthy tissue surrounding it. The margin ensures that any stray disease cells are also removed.
The removed tissue sample will be sent to a laboratory and examined under a microscope by a pathologist or dermatopathologist, a specialist trained in analyzing skin tissue. If cancer cells are found in the normal-looking skin, you will need more treatment. Often, this means another excision procedure or an additional mode of treatment.
If the removed tissue does show cancer cells in the normal-looking skin under a microscope, your treatment is complete.
Mohs surgery
In Mohs surgery, cancerous cells are removed layer by layer while leaving as much healthy skin as possible. This procedure is usually performed by a surgeon with specialized Mohs surgery training.
The surgeon begins by removing the visible squamous cell skin cancer along with a thin layer of nearby healthy-looking skin. While you wait, the tissue is examined in a lab under a microscope. If cancer cells are found at the edges of the removed skin, the surgeon will carefully take out more small sections.
This step-by-step process continues until no cancer cells remain. After the procedure, most people need stitches and additional care to help close and heal the wound.
Endoscopic endonasal approach (EEA)
At UPMC, the preferred surgical treatment for squamous cell carcinoma of the sinuses and skull base is the Endoscopic Endonasal Approach (EEA).
Pioneered and refined at UPMC, this innovative, minimally invasive technique uses the nose and nasal cavities as natural corridors to access and remove hard-to-reach or previously inoperable tumors. No open incisions are needed.
Benefits of minimally invasive EEA surgery include:
- Faster recovery time.
- No disfigurement.
- No incisions to heal.
