How Lung Cancer Is Diagnosed

In This Article

The diagnosis of lung cancer may begin with a chest X-ray, but since this test can miss early cancers, a chest CT scan, and eventually a biopsy if a nodule or mass is found, is needed. Lung cancer is often suspected after an abnormal spot is found on a chest X-ray done to evaluate a cough or chest pain. During this frightening time, it is helpful to know some of the procedures that may be recommended to find out if the abnormality is benign (non-cancerous), or malignant (cancerous). If the abnormality is malignant, further studies are done to see if the cancer has spread (metastasized) to other areas in the body and to figure out the stage of the disease.

Self Checks/At-Home Testing

Knowing your risk factors for lung cancer and getting screened when appropriate can lead to earlier detection, diagnosis, and treatment.

Lung cancer screening is available for people who meet the following criteria:

  • Are between the ages of 55 and 80
  • Smoke or smoked for a total of 30 pack-years
  • Continue to smoke or quit smoking in the past 15 years

Besides smoking, radon exposure is the second leading cause of lung cancer (and leading cause in never smokers), occupational exposures play a role in up to 27 percent of lung cancers in men, and lung cancer can run in families. Talk to your doctor about your possible risk and whether lung cancer screening would be beneficial.

It's important to note that screening is meant to be a test performed for those who do not have any symptoms. If you have any possible symptoms of lung cancer, further tests, including a full CT scan will be needed. According to the CDC, symptoms to look for include:

  • A persistent cough
  • Chest pain
  • Shortness of breath
  • Wheezing
  • Coughing up blood
  • Feeling very tired all the time
  • Unexplained weight loss

Labs and Tests

When lung cancer is suspected, a physician will first perform a thorough history and physical exam. This is done to evaluate symptoms and risk factors for lung cancer, and to look for any physical signs suggestive of lung cancer. These can include abnormal lung sounds, enlarged lymph nodes, unintentional weight loss, or clubbing of the fingernails (chubby fingernails).

Imaging tests are done to diagnose lung cancer. Non-diagnostic tests are frequently performed during the diagnosis of lung cancer as well. These can include:

  • Pulmonary function tests (PFTs): These test lung capacity and can determine how much the tumor is interfering with breathing, and sometimes, whether it is safe to perform surgery
  • Blood tests: Certain blood tests can detect biochemical abnormalities caused by lung cancers, and can also suggest spread of the tumor.


A number of different imaging studies may be needed, depending on your specific symptoms and findings on exam. These may include:

Chest X-Ray

A chest X-ray is usually the first test performed to evaluate any concerns based on a careful history and physical. This may show a mass in the lungs or enlarged lymph nodes. Sometimes the chest X-ray is normal, and further tests are needed look for a suspected lung cancer. Even if a mass is found, these are not always cancerous and further studies are needed. It should be stressed that a chest X-ray alone is not sufficient to rule out lung cancer, and early cancers can easily be missed with these tests.

CT Scan

A CT scan (computerized tomography) is frequently the second step either to follow up on an abnormal chest X-ray finding or to evaluate troublesome symptoms in those with a normal chest X-ray. CT scanning involves a series of X-rays that create a 3-dimensional view of the lungs. If the CT is abnormal, the diagnosis of lung cancer still needs confirmation through a sample of tissue by one of the procedures below.


For some people, MRI (magnetic resonance imaging) will be used to evaluate the possibility of lung cancer. This procedure uses magnetism and does not involve radiation. Certain individuals, such as those with metal implants (pacemakers, etc) should not have MRI scans. The technician will ask questions to make sure these are not present.

PET Scan

A PET scan (positron emission tomography) uses radioactive material to create colorful 3-dimensional images of a region of the body. This type of scan differs from the others in that it defines tumors that are actively growing. A small amount of radioactive sugar is injected into the bloodstream, and given time to be taken up by cells. Cells that are actively growing take up more sugar, and light up on films. The test is usually combined with a CT scan (PET/CT). As an addition to the other procedures, some researchers suggest that PET scanning may detect tumors earlier, even before they are visible anatomically through other studies. PET scans are also useful for distinguishing between tumors and scar tissue in people who have scarring in their lungs for any reason.


In a bronchoscopy, a lung specialist inserts a tube into the airways to visualize and take a sample of the tumor. This procedure is used when the tumor is found in the large airways and can be reached by the scope. Patients are given anesthesia during this procedure to minimize discomfort. During a bronchoscopy, a biopsy may be taken of any tumor or other abnormalities that are seen in the airways.

Endobronchial Ultrasound

Endobronchial ultrasound is a relatively new technique for diagnosing lung cancer. During a bronchoscopy, physicians use an ultrasound probe within the airway to examine the lungs and area between the lungs (mediastinum). For tumors that relatively close to the airways, a biopsy may be done with this imaging.

Needle Biopsy

In a fine needle aspiration (FNA) biopsy, a physician inserts a hollow needle through the chest wall, usually guided by CT visualization, to take a sample of the tumor. This can be performed for tumors that cannot be reached by bronchoscopy, especially those that are near the periphery of the lungs.


When lung cancer affects the periphery of the lungs, it can cause fluid to build up between the lungs and the lung lining (the pleura.) With local anesthesia, a larger needle is inserted into the pleural cavity from which either a diagnostic amount of fluid (small amount to test for cancer cells, a malignant pleural effusion) or a therapeutic amount of fluid (large amount to improve pain and/or shortness of breath) is removed.


A mediastinoscopy is done in the operating room under general anesthesia. A scope is inserted just above the sternum (the breast bone) into the region between the lungs (the mediastinum) to take tissue samples from lymph nodes. A PET scan can now often provide the same results that a mediastinoscopy did in the past.

Tests to Determine If Cancer Has Spread (Metastasized)

Lung cancer most commonly spreads to the liver, the adrenal glands, the brain, and the bones. Common tests include:

  • CT scan of the abdomen: To check for spread to the liver or adrenal glands
  • MRI of the brain: To look for metastases to the brain
  • Bone scan: To test for metastases to bones, especially the back, hips, and ribs
  • PET scan: A PET scan can look for metastases essentially anywhere in the body, and can sometimes replace other tests above such as a bone scan or CT scans.

Differential Diagnoses

Before the diagnosis of lung cancer, you may be feeling overwhelmed by your symptoms and any abnormality your doctor has seen or will see on an X-ray or CT scan.

A lung nodule is considered a "spot" on the lung that is 3 centimeters (an inch and a half) or less in diameter. A lung mass refers to an abnormality that is larger than 3 centimeters in diameter. A spot on the lung or a "lung lesion" could be both benign or malignant. A "shadow" on an X-ray could also be benign or malignant, or simply the overlapping of normal structures in the chest.

Lung Biopsy

If a lung cancer is suspected on imaging studies, the next step is to have a lung biopsy done to determine whether or not the abnormality is truly cancer, and to determine the type of lung cancer.

Most biopsies are done on tissue samples, but liquid biopsies are an exciting new way to follow some people with lung cancer. Approved in June of 2016, these tests can be done via a simple blood draw. At the time, they are only approved for detecting EGFR mutations, but for everyone, they are a good example of how the diagnosis and treatment of lung cancer is improving every year.

When a lung cancer spreads, it is important to "re-biopsy" tissue, as cancers can change in time, and these changes can, in turn, help you and your doctor choose the best treatment options.

Sputum Cytology

After a lung cancer is suspected based on imaging, a sample of tissue is required to confirm the diagnosis and determine the type of cancer. Sputum cytology is the easiest way to do this, but its use is limited to those tumors that extend into the airways. Sputum cytology is not always accurate and can miss some cancer cells. The test is of most benefit when positive, but says little if it is negative.

Types of Lung Cancer

There are two primary types of lung cancer. Small cell lung cancer accounts for 15 percent of cases. It tends to be aggressive and may not be found until it has already spread (especially to the brain). While it usually responds fairly well to chemotherapy, it has a poor prognosis.

Non-small cell lung cancer is most common, accounting for 80 to 85 percent of cancers. Non-small cell lung cancer is further broken down into three types:

  • Lung adenocarcinoma is the most common type of lung cancer today, responsible for half of non-small cell lung cancers. It is the most common type of lung cancer found in women, young adults, and in people who do not smoke.
  • Squamous cell carcinoma of the lungs used to be the most common type of lung cancer, but its incidence has dropped (perhaps due to more cigarettes having filters). These cancers tend to occur in or near the large airways—the first place exposed to smoke from a cigarette. Lung adenocarcinomas, in contrast, are usually found deeper in the lungs, where smoke from a filtered cigarette would settle.
  • Large cell lung cancer tends to grow in the outer regions of the lungs. These cancers are usually rapidly-growing tumors that spread quickly.

Other, less common types of lung cancer include carcinoid tumors and neuroendocrine tumors.

Molecular Profiling/Gene Testing

It's now recommended that everyone with non-small cell lung cancer, and especially lung adenocarcinoma, have molecular profiling done on their tumor. This gene testing looks for mutations in cancer cells for which specific medications are available which "target" those mutations.

These are not mutations that you are born with, nor can you pass them on to your children. They are mutations that occur in the process of a cell becoming cancerous and which "drive" the growth of a cancer.

Targeted treatments are currently approved for people with EGFR mutations, ALK rearrangementsROS1 rearrangements, and a few other mutations. In addition, other treatments are currently being studied in clinical trials.

PD-L1 Testing

Since the first immunotherapy drug was approved for the treatment of lung cancer in 2015, three additional medications have become available. A test referred to as PD-L1 may be done to determine the percent of expression of PD-L1 on your cancer cells. PD-L1 is a protein that is expressed in greater amounts on some lung cancer cells. This protein serves to enhance the "brakes" of the immune system, reducing its ability to fight off cancer cells. Some cancer cells have found ways to "overexpress" this protein as a method of hiding from the immune system. Medications known as checkpoint inhibitors work by blocking this action and essentially releasing the brakes on the immune system.

We still don't know how important PD-L1 testing will be in the treatment of lung cancer. Both lung cancers which overexpress PD-L1 and those that don't may respond to these drugs. At the current time it's thought that it may be cost-effective to do these tests, but limiting the use of these drugs only to people who have tumors that overexpress PD-L1 could reduce the number of people who would benefit from these drugs.


Careful staging—figuring out how extensive a lung cancer is—is important in designing a treatment regimen. Non-small cell lung cancer is broken down into five stages: stage 0 to stage IV. Small cell lung cancer is broken down into only two stages: limited stage and extensive stage.

A Word From Verywell

If can be frightening to have a screening test or diagnostic test turn up a spot, shadow, or nodule that needs further testing. Some people would rather not know, but this is far riskier as the cancer will simply progress and possibly spread. Earlier diagnosis and action will give you the best chance of surviving lung cancer.

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