Squamous Cell Carcinoma

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What is squamous cell carcinoma?

The most common cancer that strikes Americans is skin cancer. Of the three major types of skin cancer, squamous cell carcinoma is the second most common, after basal cell carcinoma. It accounts for around 20% of skin cancer cases. About 1 million Americans are diagnosed with squamous cell skin cancer each year.

The skin consists of three layers, with the epidermis being the outermost one. The epidermis is the layer where most skin cancers, including squamous cell carcinoma, develop. In the epidermis, cells constantly grow, divide, and make new skin cells. This process starts in the base, or basal level of the epidermis. The cells then migrate upwards through the epidermis and flatten as they go. These flat cells are squamous cells. As the cells die, the skin sheds them.

Squamous cell carcinoma, like other skin cancers, happens when excess UV (ultraviolet) light damages the DNA in skin cells. This genetic damage causes the cells to grow out of control. Sources of UV light exposure are the sun’s rays and indoor tanning beds and lights. Your risk is higher if you have light skin and hair, tend to burn rather than tan, or had bad sunburns in your youth.

Squamous cell skin cancers often start as precancerous lesions called actinic keratoses. These lesions usually appear as dry, scaly areas on highly sun-exposed areas. Once they develop into cancers, they can grow deep and may spread to lymph nodes and other areas.

The main squamous cell carcinoma treatment is surgical removal. Doctors sometimes recommend radiation therapy as well. In the early stages, this usually cures the cancer. If the cancer has spread, systemic chemotherapy and other treatments may be necessary.

Because squamous cell carcinoma can spread, it’s important to see your doctor promptly if you notice a new or changing skin lesion. If you are at high risk for developing skin cancer, you may need regular screenings with your doctor. This is also true if you have already had skin cancer. Ask your doctor how often to perform self-exams and schedule professional skin exams.

What are the symptoms of squamous cell carcinoma?

Skin cancers, including squamous cell carcinoma, usually appear on skin that gets the most sun. Most often, squamous cell carcinoma causes lesions on the face, ears, hands, arms and legs. However, skin cancers can occur anywhere, including the palms of the hands and other unexpected areas.

Common squamous cell carcinoma symptoms

Squamous cell carcinoma can appear in many different ways. It often starts as a precancerous actinic keratosis, which is a dry, rough, scaly patch. When it becomes cancerous, it most commonly looks like a red or pink raised, round growth. Squamous cell skin cancers can also be yellowish, white, brown, black or flecked. Here are other possible appearances from the American Academy of Dermatology:

  • Brown spot that resembles an age spot
  • Firm, dome-shaped growth
  • Horny growth that may look like a tiny rhinoceros horn
  • Open sore that may have a raised border and doesn’t heal or heals and returns
  • Sore that develops on an old scar
  • Wart-like growth

It’s possible to feel sensations in the area, such as itchiness, tenderness, and pins-and-needles. It can also be numb.

Sometimes, squamous cell carcinoma can affect the inside of your mouth or your nails. Inside the mouth, it can look like a sore or a white area. On the nails, it can look like a dark streak under the nail or cause the nail to disappear.

See your doctor (or schedule a telehealth visit) if you notice a new or changing spot, bump or patch on your skin. Even if you think it’s just an age spot or a pimple, check with your doctor if it persists or grows. A dermatologist has the expertise to tell you whether or not a spot is concerning. If you have a high risk of skin cancer, regular skin checks can help find potential problems early, even in precancerous stages.

What causes squamous cell carcinoma?

Like all cancers, squamous cell carcinoma starts with out-of-control cell growth. This abnormal development is the result of changes or mutations in genes that control cell growth. In some cases, people inherit these mutations. But most of the time, people acquire them spontaneously (by chance) and they accumulate over their lifetime. For the majority of cancers, scientists don’t fully understand what triggers these acquired changes.

In the case of squamous cell carcinoma, there is a known trigger. Like other types of skin cancer, excess lifelong exposure to UV light is the cause. UV light damages the DNA in skin cells a little bit with each exposure. The damage accumulates with time until it reaches the point the body can’t repair it. This damage can take years to turn into cancer. However, people with more exposures or prolonged exposures can develop cancer faster.

Causes of squamous cell carcinoma of the mouth include: excessive UV light exposure to lips, tobacco use (smoking or chewing tobacco), heavy alcohol use, and the human papillomavirus virus (HPV).

What are the risk factors for squamous cell carcinoma?

UV light exposure from the sun or indoor tanning equipment is the primary risk factor for skin cancer. People who live in areas with intense year-round sunshine tend to have a higher exposure and risk of skin cancer. Other squamous cell carcinoma risk factors include:

  • Fair skin, light eyes, and naturally light-colored hair
  • History of skin cancer or blistering sunburns when you were young
  • Presence of actinic keratoses
  • Skin that rarely tans and freckles or burns easily
  • Weakened immune system due to a medical condition or medication

Reducing your risk of squamous cell carcinoma

Since there is a known trigger for squamous cell carcinoma, it is highly preventable. The main way to lower your risk is to avoid exposure to UV light. You can take the following steps to reduce UV light exposure and the damage that leads to skin cancer:

  • Apply a daily UVA/UVB sunscreen with an SPF (sun protection factor) of 30 or more
  • Avoid indoor tanning and use a self-tanner to get the same look
  • Move activities indoors when the UV index is high
  • Schedule outdoor activities before 10 a.m. and after 4 p.m.
  • Use or create shade when outside
  • Wear protective clothing, including hats and sunglasses

It’s best to combine several of these strategies, since none of them offers total protection from UV light. This is especially true when reflection from water, sand or snow will intensify your exposure.

Your skin cancer prevention routine should also include regular skin self-exams. If you have a higher than normal risk of skin cancer, you should get professional skin checks, as well. And ask your doctor or pharmacist about the medicines you take. Find out if any of them increase your risk of burning or cause sun-sensitivity.

How is squamous cell carcinoma treated?

Squamous cell carcinoma is highly treatable and curable in the early stages. In most cases, doctors can remove the cancer in an office procedure. For actinic keratoses or very early squamous cell cancers, doctors may use cryotherapy to freeze off the lesion. However, most people will have a surgical removal with one of the following techniques:

  • Excision, which cuts out the cancer along with a ring of normal skin
  • Mohs surgery, which removes the cancer one layer at a time and examines it under a microscope. Doctors continue until no cancer cells are present microscopically. This is a common approach for cancers on the face because it removes the least amount of skin.
  • Curettage and electrodessication, which scrapes off the growth and then uses an electrical current to kill any remaining cancer cells. Doctors may use this approach on small, low-risk squamous cell cancers that are not on hairy areas, such as the scalp.

Radiation therapy is an alternative when surgery is not an option. Doctors may also recommend radiation therapy in addition to surgery.

When squamous cell carcinoma spreads, more aggressive treatment is necessary. These advanced cancers may require a combination of surgery, radiation therapy, immunotherapy, or systemic chemotherapy.

What are the potential complications of squamous cell carcinoma?

Usually, squamous cell cancer is treatable and is not life threatening. Left untreated, squamous cell carcinomas usually grow slowly, but can invade deeply. Tumor spread can deform or destroy facial structures. When they grow deep, they can damage or destroy nerves, blood vessels, and other tissues under the skin. These skin cancers can also spread to lymph nodes and other areas. Early detection and treatment increases the chances of a cure and can prevent these complications.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Jun 25
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