Diagnosis of Lung Cancer

Tests and Procedures to Diagnose Lung Cancer

doctor looking at a chest x-ray for lung cancer
How is lung cancer diagnosed and what tests and scans are done?. istockphoto.com

How do you diagnose lung cancer? 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.

Lung Cancer Screening

For those without symptoms, lung cancer screening has now been approved for early detection in people who are between the ages of 55 and 80, have smoked for at least 30 pack-years, and smoke or quit smoking within the past 15 years.

Lung "Spots"

Before going into 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. As a quick review, As a quick review, a lung nodule is considered a "spot" on the lung that is 3 cm (an inch and a half) or less in diameter. A lung mass refers to an abnormality that is larger than 3 cm 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.

History and Physical

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, or clubbing of the fingernails (chubby fingernails.)

Laboratory and Radiology Studies

  • 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.

    • CT scan (computerized tomography) - A CT scan 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.

    • MRI (magnetic resonance imaging) - In some patients, MRI 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 (positron emission tomography) - A PET scan 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. 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.

    • 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.

      • Bronchoscopy - 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.  What should I know about my bronchoscopy?

      • Needle biopsy (fine needle aspiration or FNA) With this procedure, a hollow needle is inserted 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.

      • 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.)

      • Thoracentesis - 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.

      • Mediastinoscopy - This procedure 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. This article tells you what you can expect during your mediastinoscopy.

      Test to Determine if Lung Cancer Has Spread (Metastasized)

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

      Read more about where lung cancer spreads here.

      Other Tests During Diagnosis

      Additional non-diagnostic tests are frequently performed during the diagnosis of lung cancer as well. These can include:

      • Pulmonary function tests – 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

      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.

      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 rearrangements,  ROS1 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, additional testing of your tumor 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.


      Aquiar, P., Perry, L., Penny-Dimr, J. et al. The Effect of PD-L1 Testing on the Cost-Effectiveness and Economic Impact of Immune Checkpoint Inhibitors for the Second-Line Treatment of NSCLC. Annals of Oncology. 2017 June 15. (Epub ahead of print).

      National Institute of Health. Medline Plus: Lung Cancer. Updated 05/24/17. https://medlineplus.gov/lungcancer.html