Squamous cell lung carcinoma is a subtype of non-small cell lung cancer. It’s classified based on how the cancer cells look under a microscope.

According to the American Cancer Society, most (about 80 percent) of all lung cancers are non-small cell. Among this type, about 30 percent are squamous cell carcinomas.

Squamous cell lung carcinoma begins in the top layer of cells, called squamous cells, that line the large airways (bronchi) of the lung. It usually grows in the bronchi that branch off of the main left or right bronchus in the center of the chest.

There are four subtypes of squamous cell lung carcinoma. A study of the subtypes’ DNA found the following characteristics:

  • Primitive carcinoma has the poorest outlook of the four.
  • Classical carcinoma is the most common subtype. It occurs most often in men who smoke.
  • Secretory carcinoma is slow-growing, so it doesn’t always respond well to chemotherapy.
  • Basal carcinoma is rare. It tends to occur at a relatively older age.

Of all the types of non-small cell carcinomas, squamous cell lung carcinomas have the strongest connection to smoking.

The most common symptoms of squamous cell lung carcinoma are:

  • persistent cough
  • bloody sputum
  • shortness of breath or difficulty breathing
  • sharp chest pain, especially when taking a breath
  • unexplained weight loss
  • decreased appetite
  • fatigue

Squamous cell lung carcinoma starts in the cells lining the bronchi. Over time, the cancer can spread by invading nearby lymph nodes and organs and traveling through the blood (metastasizing) to other parts of the body.

Doctors use tumor size, location, and severity of spread to classify cancer into stages. Using the TNM system, the cancer is given a number indicating tumor size (T), spread to the lymph nodes (N), and metastasis (M). These are then combined to classify the cancer into a stage.

There are six main stages. Stages 1 to 4 are subdivided according to tumor size, number, and location:

Occult stage

Occult means hidden. In this stage, there are cancer cells in the sputum, but a tumor can’t be found.

Stage 0

The cancer is only in the lining of the bronchus and not in lung tissue. This is also called carcinoma in situ.

Stage 1

The cancer is only in the lung. It hasn’t spread to the lymph nodes around it or to other parts of the body.

Stage 2

The cancer is in the lung tissue and has spread into the lining of the lung or nearby lymph nodes, but hasn’t metastasized further.

Stage 3

The cancer is in the lung tissue and has spread to nearby lymph nodes or organs, such as the esophagus or heart, but hasn’t spread to distant organs.

Stage 4

The cancer is in the lung tissue and has spread to one or more distant parts of the body. Non-small cell lung cancer most often spreads to the:

Stage 4A means the cancer has spread as one tumor, or it’s spread to the other lung or the fluid around the heart or lungs. In stage 4B, it’s metastasized as two or more tumors.

Causes of squamous cell lung carcinoma include:

Smoking

Of all the causes of squamous cell lung cancer, smoking is by far the most important. According to the , smokers are 10 times more likely to get any kind of lung cancer than people who have smoked fewer than 100 cigarettes.

The more you smoke and the longer you smoke, the higher the risk. If you quit smoking, your risk for lung cancer goes down but stays higher than for nonsmokers for several years after quitting.

The risk for getting lung cancer is almost as high for cigar and pipe smoking as for cigarettes.

Radon exposure

The U.S. Environmental Protection Agency lists radon as the second most common cause of lung cancer. It’s the most common cause of lung cancer in people who don’t smoke.

Radon is a radioactive, odorless, invisible gas that comes from rocks and soil. It’s only a problem in enclosed places, like a house, because the concentration of radon is higher. People who smoke and are exposed to radon have a much higher risk for lung cancer.

Secondhand smoke exposure

Being exposed to secondhand smoke is the third most common cause of lung cancer.

Other causes

Other causes include:

  • Long-term exposure to cancer-causing substances. Examples include asbestos, arsenic, cadmium, nickel, uranium, and some petroleum products. Exposure to these substances most often occurs at work.
  • Air pollution. Poor air quality can lead to or exacerbate certain conditions, but there are ways to protect yourself.
  • Radiation exposure. This may include previous treatment with radiation therapy to your chest or excessive exposure to radiation from getting X-rays.
  • Medical history. A personal or family history of lung cancerincreases your risk for lung cancer. If you’ve had lung cancer, you have a higher risk of getting it again. If a close relative had lung cancer, you have a higher risk of getting it.

To diagnose squamous cell lung carcinoma, your doctor will first ask you about your symptoms and do an examination.

Next, they’ll do one or more diagnostic tests depending on your history, symptoms, condition, and tumor location. These tests may include:

Lung imaging

Usually a chest X-ray is done first, then a CT scanor MRI will be done to get a better view of your lungs and look for a tumor and signs that the cancer has spread.

Obtaining some cancer cells

There are a few ways your doctor can obtain these cells. They may take a sputum sample. The fluid around your lungs usually has some cancer cells, too. Or your doctor may obtain a sample with a needle inserted through your skin (thoracentesis). Then, your cells are examined under a microscope for signs of cancer.

Biopsy

A biopsy is another way to look at cells under a microscope. Your doctor can take a biopsy of the tumor using a needle inserted through your skin (needle biopsy) or a tube with a light and camera that’s inserted through your mouth or nose (bronchoscopy).

If the cancer has spread to the lymph nodes or other structures between your lungs, your doctor can do a biopsy through an incision in your skin (mediastinoscopy).

PET scan

This is an imaging test that shows a bright spot in any tissue where there’s cancer. PET scans are used to look for metastases near the tumor or in the body.

Bone scan

This is an imaging test that shows a bright spot in areas of bonewhere the cancer has spread.

Pulmonary function tests

These test how well your lungs work. They’re used to show if you’ll have enough lung function left after surgical removal of the lung tissue with the tumor.

Treatment for squamous cell lung carcinoma depends on how advanced the cancer is, your ability to tolerate the side effects, and your overall health. Age isn’t usually a consideration.

The treatment you receive will be specific to your situation, but there are some general guidelines for the treatment of each stage.

Occult cancer

If you have cancer cells in your sputum but no cancer is found with diagnostic tests, you’ll usually undergo frequent diagnostic tests (such as a bronchoscopy or CT scan) until a tumor is found.

Stage 0

Surgical removal of the tumor and lung around it without chemotherapy or radiation therapy usually cures squamous cell carcinoma at this stage.

Stage 1

Surgery alone often works at this stage. Some lymph nodes are usually removed to see if cancer has spread to them. If the risk of the cancer coming back is high, you might receive chemotherapy after surgery. Occasionally, radiation therapy is used instead of chemotherapy.

Stage 2

This stage is usually treated with surgical removal of the tumor and lymph nodes followed by chemotherapy to kill any remaining cancer cells.

If the tumor is large, you may receive chemotherapy and radiation therapy or radiation alone before surgery to make the tumor smaller and easier to remove with surgery.

Stage 3

Surgery alone can remove some but not all of the cancer in this stage, as it’s spread to lymph nodes in your neck or vital structures in your chest. Chemotherapy and radiation therapy are usually given after surgery.

Stage 4

In this stage, cancer has spread throughout your body. Treatment depends on your overall health and how many places the cancer has spread. If you’re healthy enough to undergo surgery, you may have a combination of surgery, chemotherapy, and radiation therapy.

Other therapies that may be added to your treatment or used if surgery isn’t an option are:

If treatment won’t be effective or a person decides to stop treatment, palliative care is often given. This is supportive care used to improve the quality of life for people with advanced cancer. It can help relieve cancer symptoms as well as provide emotional support to the person with cancer and their loved ones.

Hospice is palliative care that’s given when the estimated life expectancy is less than six months.

The outcome for non-small cell lung cancers, such as squamous cell carcinoma, is better than for small cell lung carcinomas. It’s also better when it’s caught and treated early. It can even be cured if caught early enough.

The outlook for people with cancer is measured by five-year survival rates. This indicates the percentage of people who have a specific type of cancer that are alive five years or more after getting a diagnosis.

According to the American Cancer Society, the average five-year survival rates for non-small cell lung carcinoma by cancer stage are:

  • Stage 1A: 84 percent
  • Stage 2A: 60 percent
  • Stage 3A: 36 percent
  • Stage 4A: 10 percent
  • Stage 4B: less than 1 percent

It’s important to remember that these percentages are only a guide based on averages. Everyone is different.

The outlook for an individual person is influenced by many factors, such as age, general health, response to treatment, and treatment side effects. Your doctor will evaluate all of this information to give you an outlook that’s specific to you.

The percentages show that the key to having the best outlook is early detection and treatment before the cancer spreads.

You can significantly decrease your risk for lung cancer by not smoking. If you do smoke and receive a lung cancer diagnosis, survival rates tend to be better if you quit.