Squamous Cell Carcinoma (Skin Cancer)

Squamous cell carcinoma (SCC), also known as cutaneous squamous cell cancers or just squamous cell cancers, account for about 20 percent of all non-melanoma skin cancers. They start in the flat cells in the upper (outer) part of your skin, which is called the epidermis. SCCs commonly appear on sun-exposed areas of the body such as the face, ears, neck, lips, arms and backs of the hands. They can also develop in scars or chronic skin sores in other places. 

Squamous cell skin cancers can also be found in the inner lining of hollow organs, like the throat and digestive track. They sometimes start in actinic keratoses, a rough, scaly patch on the skin that develops from years of sun exposure. Less often, they form in the skin of the genital area. Squamous cell cancers can usually be removed completely (or treated in other ways), although they are much more likely than basal cell cancers to grow into deeper layers of the skin and spread to other parts of the body.

Types & Stages

The primary types of squamous cell carcinoma are:

• Squamous cell carcinoma in situ, also called Bowen disease. This is the earliest form of squamous cell skin cancer. “In situ” means that the cells of these cancers are still only in the epidermis (the upper layer of the skin) and have not invaded deeper layers. Bowen disease appears as reddish patches that tend to be large, red, scaly and sometimes crusted. Bowen disease usually doesn’t cause symptoms, although it might be itchy or sore. These patches most often appear in sun-exposed areas. Bowen disease can also occur in the skin of the anal and genital areas (where it is known as erythroplasia of Queyrat or Bowenoid papulosis). This is often related to sexually transmitted infection with human papillomaviruses (HPVs), the viruses that can also cause genital warts.
   
• Invasive squamous cell skin cancer. Squamous cell skin cancer can become invasive by growing deeper than its originating area, penetrating additional layers of the skin and potentially spreading to other parts of the body. Squamous cell skin cancer is said to be invasive if it is growing past its point of origin. The longer squamous cell skin cancer is ignored, the more time it has to become invasive, potentially burrowing deeper into nearby organs, lymph nodes and even bones. 
   
• Keratoacanthoma are dome-shaped tumors that often have a crater-like area in the middle, like a volcano. They tend to start on sun-exposed skin. They may start out growing quickly, but their growth usually slows down. Many keratoacanthomas shrink or even go away on their own over time without any treatment. But some continue to grow, and a few may even spread to other parts of the body. Many doctors view keratoacanthomas as a type of squamous cell skin cancer, although not all agree. These tumors can be hard to tell apart from SCC just by looking at them, and their growth is often hard to predict, so doctors usually advise removing or destroying them (similar to how SCCs are treated).

Signs & Symptoms

Squamous cell skin cancers can appear as:

• rough or scaly red (or darker) patches, which might crust or bleed
• raised growths or lumps, sometimes with a lower area in the center
• open sores (which may have oozing or crusted areas) that don’t heal, or that heal and then come back
• wart-like growths

Squamous cell skin cancers can also develop as a flat area showing only slight changes from normal skin. These and other types of skin cancers can also look different from the descriptions above. That’s why it’s important to have a doctor check any new or changing skin growths, sores that don’t heal, or other areas that concern you.

Diagnosis

With skin self-exams and skin checks by a doctor—including a dermatologist—squamous cell skin cancers can often be found early, making them easier to treat. Be sure to show your doctor any areas that concern you and ask them to look at areas that may be hard for you to see, like on your back.  Squamous cell skin cancers can look like a variety of marks on the skin. The key warning signs are a new growth, a spot or bump that’s getting larger over time, or a sore that doesn’t heal within a few weeks.

If you have signs or symptoms of squamous cell carcinoma, your doctor will examine you and ask you questions about your health, your lifestyle and your family history. If your doctor suspects a spot may be SCC, a biopsy will be done. Your doctor may use one of these methods:

• Local excision/excisional biopsy. The entire suspicious area is removed with a scalpel under local anesthetic. Depending on the size and location of the suspicious area, this type of biopsy may be done in a doctor's office or as an outpatient procedure at a hospital. Your doctor will put in stitches to close the excision and cover the area with a bandage.
   
• Punch biopsy. For this, a tool that looks like a tiny round cookie cutter is used to remove a deeper sample of skin. Your doctor rotates the punch biopsy tool on the skin until it cuts through all the layers. The sample is then removed, and the edges of the biopsy site are stitched together.
   
• Shave biopsy. This biopsy procedure, also known as saucerization, shaves off the top layers of the skin with a small surgical blade. Any bleeding is then stopped by putting either an ointment or a chemical that stops bleeding on it, or by using a small electrical current to seal (cauterize) the wound.

The sample of skin is sent to a pathologist, who looks at it under a microscope to check for cancer cells.

Treatment    

Treatment options for squamous cell cancer (SCC) of the skin depend on the risk of the cancer coming back, which is based on factors like the size and location of the tumor and how the cancer cells look under a microscope, as well as if a person has a weakened immune system.

• Surgery. If the tumor hasn’t already been removed in the biopsy procedure, other options are: 
   
  • Curettage and electrodesiccation: This approach might be useful in treating some small, thin SCCs that have a low risk of coming back, but it’s not usually used for larger tumors.
     
  • Shave excision: Shaving off the top layers of the skin (including the tumor) with a small surgical blade might be another option for some small SCCs that are at low risk for coming back after treatment.
     
  • Standard excision: This type of surgery, in which the tumor and a margin of normal skin around it are removed, is often used to treat SCCs.
     
  • Mohs surgery: Mohs surgery, also known as Mohs micrographic surgery or MMS, is especially useful for SCCs that are at higher risk for coming back. Mohs surgery might also be done after a standard excision if it didn’t remove all of the cancer (that is, if the surgical margins were positive). This approach is typically more complex and time-consuming than other types of surgery. Other surgical techniques similar to Mohs might also be an option in these situations.
     
• Radiation therapy. It might be an option for people with large SCCs, especially for tumors in areas where surgery would be hard to do (such as the eyelids ears, or nose), or for people who can’t have (or don’t want) surgery. Radiation isn’t often used as the first treatment for younger people with SCC because of the possible risk of long-term problems.
   
• Cryotherapy (Freezing). SCCs can be removed by freezing them with liquid nitrogen. It might be an option for some early squamous cell cancers that are at low risk for coming back, especially in people who can’t have surgery, but it’s typically not recommended for larger SCCs or those on certain parts of the nose, ears, eyelids, scalp or legs.

While it’s not common, SCC can sometimes spread to lymph nodes or distant parts of the body. If this happens, treatments that might be used include: 

• Lymph node dissection. Removing regional (nearby) lymph nodes might be recommended for some SCCs that are very large or have grown deeply into the skin, as well as if the lymph nodes feel enlarged and/or hard. The removed lymph nodes are then looked at under a microscope to see if they contain cancer cells. Sometimes, radiation therapy might be recommended after surgery.
   
• Immunotherapy. For advanced SCCs that can’t be cured with surgery or radiation therapy, one option might be using an immunotherapy drug. However, these drugs haven’t been studied in people with weakened immune systems, such as those who take medicines for autoimmune diseases or who have had an organ transplant, so the balance between benefits and risks for these people isn’t clear.
   
• Systemic chemotherapy and/or targeted therapy. Chemotherapy and targeted therapy drugs (EGFR inhibitors) might be other options for people with SCC that has spread to lymph nodes or distant organs. These types of treatment might be combined or used separately.

Causes & Risk Factors

Several risk factors make a person more likely to get squamous cell skin cancer. They include: 

• Ultraviolet (UV) light exposure to sunlight, tanning beds are another source of UV rays.
   
• Having light-colored skin. Anyone can get skin cancer, but people with light-colored skin have a much higher risk than people with naturally darker skin color. White people with fair (light-colored) skin that freckles or burns easily, blue or green eyes, and naturally red or blonde hair are at especially high risk.
   
• Albinism. This is an inherited lack of protective skin pigment. People with this condition may have pink-white skin and white hair. They have a very high risk of getting sunburns and skin cancer, so they need to be extra careful to protect their skin.
   
• Age. The risk increases as people age likely because of the buildup of sun exposure over time. But these cancers are becoming more common in younger people as well, probably for the same reason.
   
• Gender. Men are more likely than women to get squamous cell carcinoma. This is thought to be due mainly to getting more sun exposure.
   
• Exposure to certain chemicals. This includes large amounts of arsenic—an element found naturally in well water in some areas and used in making some pesticides and in some other industries. Workers exposed to coal tar, paraffin and certain types of petroleum products may also have an increased risk of skin cancer.
   
• Radiation exposure. People who have had radiation treatment have a higher risk of developing skin cancer in the area where the radiation was focused. This is particularly a concern in children who have had radiation treatment for cancer.
   
• Previous skin cancer. People who have had a basal or squamous cell cancer have a much higher chance of developing another one.
   
• Long-term or severe skin inflammation or injury. Scars from severe burns, areas of skin over serious bone infections, and skin damaged by some severe inflammatory skin diseases are more likely to develop skin cancers (mostly squamous cell cancers), although this risk is generally small.
   
• Xeroderma pigmentosum (XP). This very rare inherited condition reduces the ability of skin cells to repair DNA damage caused by sun exposure. People with this disorder often develop many skin cancers, starting in childhood.
   
• Other genetic syndromes. These have also been linked with an increased risk of skin cancer:
  • Epidermolysis bullosa
  • Fanconi anemia
  • Muir-Torre syndrome
  • Rothmund-Thomson syndrome
  • Bloom syndrome
  • Werner syndrome
     
• A weakened immune system. This can occur from certain diseases or medical treatments, including in people infected with HIV, the virus that causes AIDS. 
   
• HPV infection. Human papillomaviruses (HPVs) are a group of more than 150 viruses, many of which can cause papillomas or warts. The warts that people commonly get on their hands and feet are not related to any form of cancer. But some HPV types, especially those that affect the genital and anal areas and the skin around the fingernails, are often related to squamous cell skin cancers in these areas.
   
• Smoking. People who smoke are more likely to develop squamous cell skin cancer, especially on the lips.

Screening

With skin self-exams and skin checks by a health care professional like a dermatologist, squamous cell skin cancers can often be found early. When skin cancers are found early, they are likely to be easier to treat.