What is it?
Squamous cell carcinoma of the lung is a type of lung cancer. It occurs when abnormal lung cells multiply out of control and form a tumor. Eventually, tumor cells can spread (metastasize) to other parts of the body including the
- lymph nodes around and between the lungs
- adrenal glands
In general, there are two categories of lung cancer: small cell lung cancer and non-small cell lung cancer. The cancer cells in each type look different under the microscope. They are also treated differently. The prognosis for non-small cell lung cancer tends to be better than for small cell lung cancer; non-small cell lung cancers are more likely to be contained in one area, making treatment more likely to be successful.
Squamous cell carcinoma is one type of non-small cell lung cancer. The others are:
- large cell carcinoma.
Adenocarcinoma is the most common type of lung cancer. Squamous cell carcinoma is the second-most common type. It accounts for about 30% of all cases of non-small cell lung cancer.
Your risk of all types of lung cancer, including squamous cell carcinoma, increase if you:
- smoke. Smoking cigarettes is by far the leading risk factor for lung cancer. In fact, cigarette smokers are 13 times more likely to develop lung cancer than nonsmokers. Cigar and pipe smoking are almost as likely to cause lung cancer as cigarette smoking.
- breathe tobacco smoke. Nonsmokers who inhale fumes from cigarette, cigar, and pipe smoking have an increased risk of lung cancer.
- are exposed to radon gas. Radon is a colorless, odorless radioactive gas formed in the ground. It seeps into the lower floors of homes and other buildings and can contaminate drinking water. Radon exposure is the second leading cause of lung cancer. It's not clear whether elevated radon levels contribute to lung cancer in nonsmokers. But radon exposure does contribute to lung cancer in smokers and in people who regularly breathe high amounts of the gas at work (miners, for example). You can test radon levels in your home with a radon testing kit.
- are exposed to asbestos. Asbestos is a mineral used in insulation, fireproofing materials, floor and ceiling tiles, automobile brake linings, and other products. People exposed to asbestos on the job (miners, construction workers, shipyard workers, and some auto mechanics) have a higher-than-normal risk of lung cancer. People who live or work in buildings with asbestos-containing materials that are deteriorating also have an increased risk of lung cancer. The risk is even higher in people who also smoke. Asbestos exposure also increases the risk of developing mesothelioma. It's a relatively rare and usually fatal cancer that starts in the lining of the lungs.
- are exposed to other cancer-causing agents at work. These include uranium, arsenic, vinyl chloride, nickel chromates, coal products, mustard gas, chloromethyl ethers, gasoline, and diesel exhaust.
Most cases of squamous cell carcinoma start in the center of the lungs. These tumors may cause some symptoms, such as coughing up blood, at an earlier stage than tumors on the edges of the lungs, such as adenocarcinomas.
Squamous cell carcinoma often spreads (metastasizes) to other parts of the body because of the constant flow of fluids (blood and lymph) through the lungs. The fluids can carry cancer cells to nearby areas, such as the chest wall, neck, esophagus, and the protective sac around the heart. Unless it is diagnosed and treated early, it often spreads throughout the body.
Some lung cancers have the ability to secrete chemicals that circulate in the bloodstream. These chemicals can change the way the body functions. Squamous cell lung cancer may secrete a substance that leads to abnormally high blood calcium levels. This can cause dehydration, constipation, kidney problems and confusion.
Early on, squamous cell lung cancer may have no symptoms. If symptoms occur, they may include:
- a cough that doesn't go away
- coughing up blood or mucus
- shortness of breath or trouble breathing
- discomfort when swallowing
- chest pain
- unexplained weight loss
- poor appetite
- high levels of calcium in the blood.
If the cancer has spread beyond the lungs, it can cause other symptoms. For example, you may have bone pain if it has spread to your bones, or headaches and seizures if it has spread to your brain.
Many of these symptoms can be caused by other conditions. See your doctor if you have symptoms so that the problem can be diagnosed and properly treated.
Your doctor may suspect lung cancer based on:
- your symptoms
- your smoking history
- whether you live with a smoker
- your exposure to asbestos and other cancer-causing agents.
To look for evidence of cancer, your doctor will examine you, paying special attention to your throat, neck, lymph nodes and lungs. He or she will order imaging tests to check your lungs for masses. In most cases, a chest x-ray will be done first. If the x-ray shows anything suspicious, a CT scan will be done. As the scanner moves around you, it takes many pictures. A computer then combines the images. This creates a more detailed image of the lungs, allowing doctors to confirm the size and location of a mass or tumor.
You may also have a magnetic resonance imaging (MRI) scan or a positron emission tomography (PET) scan. MRI scans provide detailed pictures of the body's organs, but they use radio waves and magnets to create the images, not x-rays. PET scans look at the function of tissue rather than anatomy. Lung cancer tends to show intense metabolic activity on a PET scan. Some medical centers offer combined PET-CT scanning.
If cancer is suspected based on these images, more tests will be done to make the diagnosis, determine the type of cancer, and see if it has spread. These tests may include the following:
- Sputum sample. Coughed-up mucus is checked for cancer cells.
- Biopsy. A sample of abnormal lung tissue is removed and examined under a microscope in a laboratory. If the tissue contains cancer cells, the type of cancer can be determined by the way the cells look under the microscope. The tissue is often obtained during a bronchoscopy. However, surgery may be necessary to expose the suspicious area.
- Bronchoscopy. During this procedure, a tube-like instrument is passed down the throat and into the lungs. A camera on the end of the tube allows doctors to look for cancer. Doctors can remove a small piece of tissue for a biopsy.
- Mediastinoscopy. In this procedure, a tube-like instrument is used to biopsy lymph nodes or masses between the lungs. (This area is called the mediastinum.) A biopsy obtained this way can diagnose the type of lung cancer and determine whether the cancer has spread to lymph nodes.
- Fine-needle aspiration. With a CT scan, a suspicious area can be identified. A tiny needle is then inserted into that part of the lung or pleura. The needle removes a bit of tissue for examination in a laboratory. The type of cancer can then be diagnosed.
- Thoracentesis. If there is fluid build-up in the chest, it can be drained with a sterile needle. The fluid is then checked for cancer cells.
- Video-assisted thoracoscopic surgery (VATS). In this procedure, a surgeon inserts a flexible tube with a video camera on the end into the chest through an incision. He or she can then look for cancer in the space between the lungs and the chest wall and on the edge of the lung. Abnormal lung tissue can also be removed for a biopsy.
- Additional imaging tests to look for cancer spread. These imaging tests can detect lung cancer that has spread to the bones, brain, or other parts of the body.
Occasionally, surgery is done to remove the tumor first; the diagnosis is made after the tumor has been examined in a laboratory.
After the cancer has been diagnosed, it is assigned a "stage." The stages of squamous cell carcinoma reflect the tumor's size and how far the cancer has spread. Stages I through III are further divided into A and B categories.
- Stage I tumors are small and have not invaded the surrounding tissue or organs.
- Stage II and III tumors have invaded surrounding tissue and/or organs and have spread to lymph nodes.
- Stage IV tumors have spread beyond the chest.
Squamous cell lung cancer will continue to grow until it is treated. As with any cancer, even if it seems to be cured after treatment, this lung cancer can return.
To reduce your risk of squamous cell lung cancer:
- Don't smoke. If you already smoke, talk to your doctor about getting the help you need to quit.
- Avoid secondhand smoke. Choose smoke-free restaurants and hotels. Ask guests to smoke outdoors, especially if there are children in your home.
- Reduce exposure to radon. Have your home checked for radon gas. A radon level above 4 picocuries/liter is unsafe. If you have a private well, have your drinking water checked, too. Kits to test for radon are widely available.
- Reduce exposure to asbestos. Because there is no safe level of asbestos exposure, any exposure is too much. If you have an older home, check to see if any insulation or other asbestos-containing material is exposed or deteriorating. The asbestos in these areas must be professionally removed or sealed up. If the removal isn't done properly, you may be exposed to more asbestos than you would have been if it had been left alone. People who work with asbestos-containing materials should use approved measures to limit their exposure and to prevent bringing asbestos dust home on their clothing.
The U.S. Preventive Services Task Force recommends annual screening for lung cancer with low-dose computed tomography in adults ages 50 to 80 years if you:
- Have a 20 pack-year smoking history (pack years is calculated by multiplying the number of cigarettes smoked per day times the number of years you smoked), AND
- Currently smoke or have quit within the past 15 years, AND
- Are healthy enough to undergo lung cancer surgery.
The decision to proceed with lung cancer screening is not straightforward. Many so-called abnormalities found on CT scan are not cancerous. However patients will often undergo extensive testing, including surgery, to find out. CT scan screening is an individualized decision to be made with your doctor.
Treatment depends on the cancer's stage as well as the patient's condition, lung function, and other factors. (Some patients may have other lung conditions, such as emphysema or COPD—chronic obstructive pulmonary disease.) If the cancer has not spread, surgery is usually the treatment of choice. There are three types of surgery:
- Wedge resection removes only a small part of the lung
- Lobectomy removes one lobe of the lung
- Pneumonectomy removes an entire lung.
Lymph nodes are also removed and examined to see if the cancer has spread.
Some surgeons use video-assisted thoracoscopy (VATS) to remove small, early-stage tumors, especially if the tumors are near the outer edge of the lung. (VATS can also be used to diagnose lung cancer.) Because the incisions for VATS are small, this technique is less invasive than a traditional "open" procedure.
Because surgery will remove part or all of a lung, breathing may be more difficult afterwards, especially in patients with other lung conditions (emphysema, for example). Doctors can test lung function prior to surgery and predict how it might be affected by surgery.
Depending on how far the cancer has spread, treatment may include chemotherapy (the use of anticancer drugs) and radiation therapy. These may be given before and/or after surgery. Unfortunately, squamous cell carcinoma does not respond to chemotherapy and radiation therapy as well as other types of tumors.
When the tumor has spread significantly, chemotherapy and/or immunotherapy may be recommended to slow its growth, even if it cannot cure the disease. These therapies have been shown to ease symptoms and prolong life in cases of advanced lung cancer. Radiation therapy can relieve symptoms, too. It is often used to treat lung cancer that has spread to the brain or bones and is causing pain. It can also be used alone or with chemotherapy to treat the lung cancer that is confined to the chest.
People who may not withstand surgery due to other serious medical problems may receive radiation therapy, with or without chemotherapy, to shrink the tumor.
Cancerous tissue may be tested for specific genetic abnormalities (mutations). Doctors may then be able to treat the cancer with a "targeted therapy." These therapies can derail the cancer's growth by preventing or changing chemical reactions linked to particular mutations. For example, some target therapies prevent cancer cells from receiving chemical "messages" telling them to grow. However, these specific mutations tend to occur less frequently in squamous cell cancers compared to adenocarcinomas.
Knowing about specific genetic mutations can help predict which therapy will be best. This strategy can be especially helpful in certain patients, such as women with adenocarcinoma of the lung who have never smoked.
Even after treatment has been completed, lung cancer patients must return for regular follow-up appointments. Even if the cancer was initially placed into remission," it can return months or even years later.
When to call a professional
If you have any of symptoms of squamous cell lung cancer, see your doctor as soon as possible.
Squamous cell lung cancer usually is diagnosed after the disease has spread, so the prognosis is often guarded. The survival rate is significantly higher if the disease is detected and treated early.
Even when surgery and other therapies are initially successful, squamous cell lung cancer can return. This is because cancer cells can start to spread without being detected right away.
National Cancer Institute (NCI)
American Cancer Society (ACS)
American Lung Association
National Heart, Lung, and Blood Institute (NHLBI)
U.S. Environmental Protection Agency (EPA)
National Institute for Occupational Safety and Health