Some lung cancers can be found by screening, but most lung cancers are found because they are causing problems. If you have possible signs or symptoms of lung cancer, see your doctor, who will examine you and may order some tests. The actual diagnosis of lung cancer is made by looking at a sample of lung cells under a microscope.
Medical history and physical exam
Your doctor will ask about your medical history to learn about your symptoms and possible risk factors. Your doctor will also examine you to look for signs of lung cancer or other health problems.
If the results of your history and physical exam suggest you might have lung cancer, more tests will be done. These could include imaging tests and/or getting biopsies of lung tissue.
Imaging tests use x-rays, magnetic fields, sound waves, or radioactive substances to create pictures of the inside of your body. Imaging tests may be done for a number of reasons both before and after a diagnosis of lung cancer, including:
- To look at suspicious areas that might be cancer
- To learn how far cancer may have spread
- To help determine if treatment is working
- To look for possible signs of cancer coming back after treatment
This is often the first test your doctor will do to look for any abnormal areas in the lungs. Plain x-rays of your chest can be done at imaging centers, hospitals, and even in some doctors’ offices. If something suspicious is seen, your doctor may order more tests.
Computed tomography (CT) scan
A CT scan uses x-rays to make detailed cross-sectional images of your body. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you while you lie on a table. A computer then combines these pictures into images of slices of the part of your body being studied.
A CT scan is more likely to show lung tumors than routine chest x-rays. It can also show the size, shape, and position of any lung tumors and can help find enlarged lymph nodes that might contain cancer that has spread from the lung. This test can also be used to look for masses in the adrenal glands, liver, brain, and other internal organs that might be due to the spread of lung cancer.
CT-guided needle biopsy: If a suspected area of cancer is deep within your body, a CT scan can be used to guide a biopsy needle into the suspected area.
Magnetic resonance imaging (MRI) scan
Like CT scans, MRI scans provide detailed images of soft tissues. But MRI scans use radio waves and strong magnets instead of x-rays. A contrast material called gadolinium is often injected into a vein before the scan to better see details.
MRI scans are most often used to look for possible spread of lung cancer to the brain or spinal cord. Rarely, MRI of the chest may be done to see if the cancer has grown into central structures in the chest.
Positron emission tomography (PET) scan
For this test, a form of radioactive sugar (known as FDG) is injected into the blood. Because cancer cells in the body are growing quickly, they absorb more of the radioactive sugar. This radioactivity can be seen with a special camera.
PET/CT scan: Often a PET scan is combined with a CT scan using a special machine that can do both at the same time. This lets the doctor compare areas of higher radioactivity on the PET scan with the more detailed appearance of that area on the CT scan. This is the type of PET scan most often used in patients with lung cancer.
If you appear to have early stage lung cancer, your doctor can use this test to help see if the cancer has spread to nearby lymph nodes or other areas, which can help determine if surgery may be an option for you. This test can also be helpful in getting a better idea if an abnormal area on another imaging test might be cancer.
PET/CT scans can also be useful if your doctor thinks the cancer might have spread but doesn’t know where. They can show spread of cancer to the liver, bones, adrenal glands, or some other organs. They are not as useful for looking at the brain, since all brain cells use a lot of glucose.
PET/CT scans are often helpful in diagnosing lung cancer, but their role in checking whether treatment is working is unproven. Most doctors do not recommend PET/CT scans for routine follow up of patients with lung cancer after treatment.
For this test, a small amount of low-level radioactive material is injected into the blood. The substance settles in areas of bone changes throughout the entire skeleton. This radioactivity can be seen with a special camera.
A bone scan can help show if a cancer has spread to the bones. But this test isn’t needed very often because PET scans, which are often done in patients with non-small cell lung cancer, can usually show if cancer has spread to the bones. Bone scans are done mainly when there is reason to think the cancer may have spread to the bones (because of symptoms such as bone pain) and other test results aren’t clear.
Tests for diagnosing lung cancer
Symptoms and the results of certain tests may strongly suggest that a person has lung cancer, but the actual diagnosis is made by looking at lung cells with a microscope.
The cells can be taken from lung secretions (sputum or phlegm), fluid removed from the area around the lung (thoracentesis), or from a suspicious area using a needle or surgery (known as a biopsy). The choice of which test(s) to use depends on the situation.
A sample of mucus you cough up from the lungs (sputum) is looked at under a microscope to see if it has cancer cells. The best way to do this is to get early morning samples from you 3 days in a row. This test is more likely to help find cancers that start in the major airways of the lung, such as squamous cell lung cancers. It may not be as helpful for finding other types of non-small cell lung cancer. If your doctor suspects lung cancer, further testing will be done even if no cancer cells are found in the sputum.
If there is a buildup of fluid around the lungs (called a pleural effusion), doctors can perform thoracentesis to find out if it is caused by cancer spreading to the lining of the lungs (pleura). The buildup might also be caused by other conditions, such as heart failure or an infection.
For this procedure, the skin is numbed and a hollow needle is inserted between the ribs to drain the fluid. (In a similar test called pericardiocentesis, fluid is removed from within the sac around the heart.) The fluid is checked under a microscope for cancer cells. Chemical tests of the fluid are also sometimes useful in telling a malignant (cancerous) pleural effusion from one that is not.
If a malignant pleural effusion has been diagnosed, thoracentesis may be repeated to remove more fluid. Fluid buildup can keep the lungs from filling with air, so thoracentesis can help a person breathe better.
Doctors can often use a hollow needle to get a small sample from a suspicious area (mass).
- In a fine needle aspiration (FNA) biopsy, the doctor uses a syringe with a very thin, hollow needle to withdraw (aspirate) cells and small fragments of tissue.
- In a core biopsy, a larger needle is used to remove one or more small cores of tissue. Samples from core biopsies are larger than FNA biopsies, so they are often preferred.
An advantage of needle biopsies is that they don’t require a surgical incision. The drawback is that they remove only a small amount of tissue. In some cases (particularly with FNA biopsies), the amount removed might not be enough to both make a diagnosis and to classify DNA changes in the cancer cells that can help doctors choose anticancer drugs.
Transthoracic needle biopsy: If the suspected tumor is in the outer part of the lungs, the biopsy needle can be inserted through the skin on the chest wall. The area where the needle is to be inserted may be numbed with local anesthesia first. The doctor then guides the needle into the area while looking at the lungs with either fluoroscopy (which is like an x-ray, but creates a moving image on a screen rather than a single picture on film) or CT scans.
If CT is used, the needle is inserted toward the mass (tumor), a CT image is taken, and the direction of the needle is guided based on the image. This is repeated a few times until the needle is within the mass.
A possible complication of this procedure is that air may leak out of the lung at the biopsy site and into the space between the lung and the chest wall. This is called a pneumothorax. It can cause part of the lung to collapse and possibly trouble breathing. If the air leak is small, it often gets better without any treatment. Large air leaks are treated by putting a small tube into the chest space and sucking out the air over a day or two, after which it usually heals on its own.
Other approaches to needle biopsies: An FNA biopsy may also be done to check for cancer in the lymph nodes between the lungs:
- Transtracheal FNA or transbronchial FNA is done by passing the needle through the wall of the trachea (windpipe) or bronchi (the large airways leading into the lungs) during bronchoscopy or endobronchial ultrasound (described below).
- In some patients an FNA biopsy is done during endoscopic esophageal ultrasound (described below) by passing the needle through the wall of the esophagus.
Bronchoscopy can help the doctor find some tumors or blockages in the larger airways of the lungs, which can often be biopsied during the procedure.
For this exam, a lighted, flexible fiber-optic tube (called a bronchoscope) is passed through the mouth or nose and down into the windpipe and bronchi. The mouth and throat are sprayed first with a numbing medicine. You may also be given medicine through an intravenous (IV) line to make you feel relaxed.
Small instruments can be passed down the bronchoscope to take biopsy samples. The doctor can also sample cells from the lining of the airways with a small brush (bronchial brushing) or by rinsing the airways with sterile saltwater (bronchial washing). These tissue and cell samples are then looked at under a microscope.
Tests to find lung cancer spread in the chest
If lung cancer has been found, it’s often important to know if it has spread to the lymph nodes in the space between the lungs (mediastinum) or other nearby areas. This can affect a person’s treatment options. Several types of tests can be used to look for this cancer spread.
Ultrasound is a type of imaging test that uses sound waves to create pictures of the inside of your body. For this test, a small, microphone-like instrument called a transducer gives off sound waves and picks up the echoes as they bounce off body tissues. The echoes are converted by a computer into an image on a computer screen.
For endobronchial ultrasound, a bronchoscope is fitted with an ultrasound transducer at its tip and is passed down into the windpipe. This is done with numbing medicine (local anesthesia) and light sedation.
The transducer can be pointed in different directions to look at lymph nodes and other structures in the mediastinum (the area between the lungs). If suspicious areas such as enlarged lymph nodes are seen on the ultrasound, a hollow needle can be passed through the bronchoscope and guided into these areas to obtain a biopsy. The samples are then sent to a lab to be looked at under a microscope.
Endoscopic esophageal ultrasound
This test is like endobronchial ultrasound, except the doctor passes an endoscope (a lighted, flexible scope) down the throat and into the esophagus (the tube connecting the throat to the stomach). This is done with numbing medicine (local anesthesia) and light sedation.
The esophagus is just behind the windpipe and is close to some lymph nodes inside the chest to which lung cancer may spread. As with endobronchial ultrasound, the transducer can be pointed in different directions to look at lymph nodes and other structures inside the chest that might contain lung cancer. If enlarged lymph nodes are seen on the ultrasound, a hollow needle can be passed through the endoscope to get biopsy samples of them. The samples are then sent to a lab to be looked at under a microscope.
Mediastinoscopy and mediastinotomy
These procedures may be done to look more directly at and get samples from the structures in the mediastinum (the area between the lungs). They are done in an operating room by a surgeon while you are under general anesthesia (in a deep sleep). The main difference between the two is in the location and size of the incision.
Mediastinoscopy: A small cut is made in the front of the neck and a thin, hollow, lighted tube is inserted behind the sternum (breast bone) and in front of the windpipe to look at the area. Instruments can be passed through this tube to take tissue samples from the lymph nodes along the windpipe and the major bronchial tube areas. Looking at the samples under a microscope can show if they have cancer cells.
Mediastinotomy: The surgeon makes a slightly larger incision (usually about 2 inches long) between the left second and third ribs next to the breast bone. This lets the surgeon reach some lymph nodes that can’t be reached by mediastinoscopy.
Thoracoscopy can be done to find out if cancer has spread to the spaces between the lungs and the chest wall, or to the linings of these spaces. It can also be used to sample tumors on the outer parts of the lungs as well as nearby lymph nodes and fluid, and to assess whether a tumor is growing into nearby tissues or organs. This procedure is not often done just to diagnose lung cancer, unless other tests such as needle biopsies are unable to get enough samples for the diagnosis.
Thoracoscopy is done in the operating room while you are under general anesthesia (in a deep sleep). A small cut (incision) is made in the side of the chest wall. (Sometimes more than one cut is made.) The doctor then puts a thin, lighted tube with a small video camera on the end through the incision to view the space between the lungs and the chest wall. Using this, the doctor can see possible cancer deposits on the lining of the lung or chest wall and remove small pieces of tissue for examination. (When certain areas can’t be reached with thoracoscopy, the surgeon may need to make a larger incision in the chest wall, known as a thoracotomy.)
Thoracoscopy can also be used as part of the treatment to remove part of a lung in some early-stage lung cancers. This type of operation, known as video-assisted thoracic surgery (VATS), is described in more detail in Surgery for non-small cell lung cancer.
Lab tests of biopsy and other samples
Samples that have been collected during biopsies or other tests are sent to a pathology lab. A pathologist, a doctor who uses lab tests to diagnose diseases such as cancer, will look at the samples with a microscope and may do other special tests to help better classify the cancer. (Cancers from other organs can spread to the lungs. It’s very important to find out where the cancer started, because treatment is different depending on the type of cancer.)
The results of these tests are described in a pathology report, which is usually available within about a week. If you have any questions about your pathology results or any diagnostic tests, talk to your doctor. If needed, you can get a second opinion of your pathology report by having your tissue samples sent to a pathologist at another lab.
For more information on understanding your pathology report, see the Lung Pathology section of our website.
For this test, very thin slices of the samples are attached to glass microscope slides. The samples are then treated with special proteins (antibodies) that attach only to a specific substance found in certain cancer cells. If the cancer cells have that substance, the antibody will attach to the cells. Chemicals are then added so that antibodies change color. The doctor who looks at the sample under a microscope can see this color change.
In some cases, doctors may look for specific gene changes in the cancer cells that could mean certain targeted drugs might help treat the cancer. For example:
- The epidermal growth factor receptor (EGFR) is a protein that sometimes appears in high amounts on the surface of cancer cells and helps them grow. Some drugs that target EGFR seem to work best against lung cancers with certain changes in the EGFR gene, which are more common in certain groups, such as non-smokers, women, and Asians. But these drugs don’t seem to be as helpful in patients whose cancer cells have changes in the KRAS gene. Many doctors now test for changes in genes such as EGFR and KRAS to determine if these newer treatments are likely to be helpful.
- About 5% of non-small cell lung cancers (NSCLCs) have a change in a gene called ALK. This change is most often seen in non-smokers (or light smokers) who have the adenocarcinoma subtype of NSCLC. Doctors may test cancers for changes in the ALK gene to see if drugs that target this change may help them.
- About 1% to 2% of NSCLCs have a rearrangement in the ROS1 gene, which might make the tumor respond to certain targeted drugs. A similar percentage have a rearrangement in the RET gene. Certain drugs that target cells with RET gene changes might be options for treating these tumors.
Newer lab tests for certain other genes or proteins may also help guide the choice of treatment. Some of these are described in What’s new in non-small cell lung cancer research and treatment?
Blood tests are not used to diagnose lung cancer, but they can help to get a sense of a person’s overall health. For example, they can be used to help determine if a person is healthy enough to have surgery.
A complete blood count (CBC) looks at whether your blood has normal numbers of different types of blood cells. For example, it can show if you are anemic (have a low number of red blood cells), if you could have trouble with bleeding (due to a low number of blood platelets), or if you are at increased risk for infections (because of a low number of white blood cells). This test will be repeated regularly if you are treated with chemotherapy, because these drugs can affect blood-forming cells of the bone marrow.
Blood chemistry tests can help spot abnormalities in some of your organs, such as the liver or kidneys. For example, if cancer has spread to the liver and bones, it may cause abnormal levels of certain chemicals in the blood, such as a high level of lactate dehydrogenase (LDH).
Pulmonary function tests
Pulmonary function tests (PFTs) are often done after lung cancer is diagnosed to see how well your lungs are working (for example, how much emphysema or chronic bronchitis is present). This is especially important if surgery might be an option in treating the cancer. Surgery to remove lung cancer may mean removing part or all of a lung, so it’s important to know how well the lungs are working beforehand. Some people with poor lung function (like those with lung damage from smoking) don’t have enough lung reserve to withstand removing even part of a lung. These tests can give the surgeon an idea of whether surgery is a good option, and if so, how much lung can safely be removed.
There are different types of PFTs, but they all basically have you breathe in and out through a tube that is connected to a machine that measures airflow.
Sometimes PFTs are coupled with a test called an arterial blood gas. In this test, blood is removed from an artery (instead of from a vein, like most other blood tests) to measure the amount of oxygen and carbon dioxide that it contains.
Last Revised: 02/08/2016