What is Squamous Cell Carcinoma?

What is Squamous Cell Carcinoma?

Squamous cells are found near the skin’s surface and protect the tissue underneath it. Squamous cell carcinoma, also known as cutaneous squamous cell carcinoma, is a slow-growing cancer that occurs in the middle and outer layers of the skin.

The second most common form of skin cancer, squamous cell carcinoma is often the result of prolonged, unprotected exposure to ultraviolet radiation from the sun.

Squamous cell carcinoma is usually found on sun-exposed areas of the body (such as the face, ears, and back of the hands) and is generally not life-threatening. As it progresses, squamous cell carcinoma can grow quite deep, injuring nerves and blood vessels and eventually forming large tumors.

Stages of Squamous Cell Carcinoma


Stages of squamous cell carcinomas are determined by tumor size and how the cancer spreads (if at all.) The TNM (Tumor/Nodes/Metastasis) system is used for staging this type of cancer.

  • Stage 0 - Stage 0 cancer is only found in the epidermis. The original tumor is contained in the uppermost layer of the skin and has not spread below the dermis. At this stage, squamous cell carcinoma is also referred to as carcinoma in situ. Stage 0 cancers often appear as red or pink scaly patches.
  • Stage 1 - Stage 1 tumors are no larger than 2 centimeters across. Tumors may have spread to the skin's next layer, the dermis, but have not gone deeper to the muscle or bone. Cancer has not spread to the lymph nodes or other organs in the body.
  • Stage 2 - Stage 2 tumors are larger than 2 centimeters wide but no more than 4 cm in most significant dimension. Tumors may have spread to the dermis, but cancer has not reached any muscle or bone at this stage. Tumors have also not spread to lymph nodes or other body organs. A tumor of any size will be classified as Stage 2 when there are two or more accompanying high-risk factors, such as spreading into the skin's lower layers or reaching the nerves.
  • Stage 3 - Stage 3 cancer has spread to deeper areas, such as invading muscle or bone, or has spread to lymph nodes near the original tumor. However, tumors at this stage have not spread to other body organs.
  • Stage 4 - Stage 4 cancers may be any size and may have spread to lymph nodes nearby the original tumor. They may also have spread to far away areas such as other organs, including the brain or lungs.

At the earlier stages, the five-year survival rate for squamous cell carcinoma is very high at 99%. Even when cancer spreads to the nearby lymph nodes, effective treatment is possible. This rate drops to less than 50% once squamous cell carcinoma spreads beyond the skin.

Signs & Symptoms of Squamous Cell Carcinoma


Squamous cell carcinoma often occurs on sun-exposed areas of the skin such as the scalp, back of the hands, ears, or lips. For this reason, there are often noticeable signs of sun damage before squamous cell carcinoma develops. It can occur anywhere on the body.

Signs and symptoms of squamous cell carcinoma of the skin include:

  • A firm, red lump on the skin
  • A flat sore with a scaly crust
  • A new sore or raised area on an old scar or ulcer
  • A rough, scaly patch on one of the lips that may turn into an open sore
  • A red sore or rough patch inside the mouth
  • A red, raised patch or wart-like sore on the genitals or on/in the anus

What Causes Squamous Cell Carcinoma?


Squamous cells are the flat outer cells of the middle and outer layers of the skin. These cells are constantly being shed as new cells are formed. Unprotected and prolonged exposure to ultraviolet radiation found in sunlight, commercial tanning lamps, and tanning beds can cause changes (mutations) in the DNA of squamous cells. Squamous cell carcinoma develops as these mutated cells grow out of control and replace healthy cells.

What Causes Squamous Cell Carcinoma?

Risk Factors

Understanding what can cause DNA damage to squamous cells in the skin can help you detect the disease early or prevent it from happening. Risk factors for developing squamous cell carcinoma include the following:

  • Unprotected and prolonged exposure to ultraviolet radiation - From the sun or from tanning booths or beds
  • A weakened immune system –May be due to either illness or certain immunosuppressive medication use
  • Fair skin
  • Age over 50
  • Gender - Squamous cell carcinoma is more common among men
  • A history of previous skin cancer - Including basal cell carcinoma
  • A history of skin precancers - Including actinic keratosis and other precancerous lesions
  • A history of chronic infections and skin inflammation - From burns (including sunburns), scars, and other skin conditions
  • A history of sun-sensitive conditions - Including xeroderma and pigmentosum
  • A history of human papillomavirus (HPV)



Exposure to the sun's ultraviolet radiation accumulates over the years. The best approach to preventing squamous cell carcinoma is comprehensive and includes the following:

  • Stay in the shade or avoid the sun between 10 AM and 4 PM, when the UV rays are strongest
  • Avoid tanning, including the use of UV tanning booths or tanning beds which are at least as harmful as natural sun UV rays
  • Use broad-spectrum (UVA/UVB) sunscreen with an SPF of 30 or higher. Re-apply often when outside for prolonged periods and/or after swimming or excessive sweating.
  • Wear sunscreen year-round, as ultraviolet radiation is as dangerous in the other seasons as it is in the summer
  • Wear protective clothing, including sunglasses and broad-brimmed hats
  • Examine your skin regularly. Check your skin monthly, head-to-toe.
  • See a dermatologist every year for a professional skin exam
Get Care

Trust NewYork-Presbyterian for Squamous Cell Carcinoma Care

Learning about the diagnosis and treatment options available is the first step if you have questions or are experiencing squamous cell carcinoma symptoms.

NewYork-Presbyterian provides advanced care for all types and stages of skin cancer, including squamous cell carcinoma. Our team of cancer experts offers treatment options ranging from minimally invasive surgical procedures to advanced therapies and clinical trials. Contact us today for an appointment.