Lung cancer

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Diagnosis of lung cancer

Diagnosis is the process of finding out the cause of a health problem. Diagnosing lung cancer usually begins with a visit to your family doctor. Your doctor will ask you about any symptoms you have and may do a physical exam. Based on this information, your doctor may refer you to a specialist or order tests to check for lung cancer or other health problems.

The process of diagnosis may seem long and frustrating. It’s normal to worry, but try to remember that other health conditions can cause similar symptoms as lung cancer. It’s important for the healthcare team to rule out other reasons for a health problem before making a diagnosis of lung cancer.

The following tests are commonly used to rule out or diagnose lung cancer. Many of the same tests used to diagnose cancer are used to find out the stage (how far the cancer has progressed). Your doctor may also order other tests to check your general health and to help plan your treatment.

Health history and physical exam

Your health history is a record of your symptoms, risk factors and all the medical events and problems you have had in the past. Your doctor will ask questions about your history of:

  • symptoms that suggest lung cancer
  • smoking or breathing in second-hand smoke
  • being around radon gas
  • being around asbestos at work
  • lung cancer or lung diseases
  • radiation therapy to the chest area

Your doctor may also ask about a family history of:

  • lung cancer
  • other cancers

A physical exam allows your doctor to look for any signs of lung cancer. During a physical exam, your doctor may:

  • listen to your lungs and heart using a stethoscope
  • tap your chest to listen for sounds
  • feel your neck and area above the collarbone to look for swelling or lymph nodes that are larger than normal
  • feel your abdomen for a liver that is larger than normal
  • check your blood pressure and pulse

Find out more about physical exams.

Complete blood count (CBC)

A CBC measures the number and quality of white blood cells, red blood cells and platelets. A CBC is done to get some basic information about your overall health before any treatments start.

Find out more about a complete blood count.

Blood chemistry tests

Blood chemistry tests measure certain chemicals in the blood. They show how well certain organs are functioning and can help find abnormalities. Blood chemistry tests are used to see if lung cancer has spread to other parts of the body.

Alkaline phosphatase (ALP), calcium or phosphorus levels that are higher than normal may mean that cancer has spread to the bones.

Liver function tests look at the levels of lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate transaminase (AST) and bilirubin. Higher levels may mean that cancer has spread to the liver.

Find out more about blood chemistry tests.


An x-ray uses small doses of radiation to make an image of parts of the body on film. A chest x-ray is often the first imaging test done to look for problems with the lungs. It may show any spots, tumours or changes in the lungs.

Find out more about x-rays.

CT scan

A computed tomography (CT) scan uses special x-ray equipment to make 3-D and cross-sectional images of organs, tissues, bones and blood vessels inside the body. A computer turns the images into detailed pictures.

A CT scan is used to:

  • show the location, size and shape of a lung tumour
  • find any lymph nodes in the chest that are larger than normal
  • look for any spread of the tumour to other parts of the body
  • guide a biopsy

Find out more about CT scans.

PET scan

A positron emission tomography (PET) scan uses radioactive materials called radiopharmaceuticals to look for changes in the metabolic activity of body tissues. A computer analyzes the radioactive patterns and makes 3-D colour images of the area being scanned.

A PET scan is used to find out how far the lung cancer has spread as it looks at the whole body during th scan. It can find tumours over 8 mm in size. It is more accurate than CT scan for finding spread to the lymph nodes in the middle of the chest (mediastinum) and other areas of the body. PET scans are not used to look at the brain, because the brain has a high level of metabolic activity.  

Find out more about PET scans.


Magnetic resonance imaging (MRI) uses powerful magnetic forces and radiofrequency waves to make cross-sectional images of organs, tissues, bones and blood vessels. A computer turns the images into 3-D pictures.

An MRI is used to look at the brain to see if cancer has spread there. It may also be used to look at the heart before surgery to find out if the cancer has invaded the heart or the large blood vessels and nerves at the tip of the lung.

Find out more about MRIs.


An ultrasound uses high-frequency sound waves to make images of structures in the body. It is used to look for a buildup of fluid around the lungs. An ultrasound is also used to guide a biopsy during endoscopic procedures.

Find out more about ultrasounds.


During a biopsy, the doctor removes tissue or cells from the body so they can be tested in a lab. A report from the pathologist will confirm whether or not cancer cells are found in the sample and identify the type of lung cancer. Getting enough tissue during a biopsy is important so that immunohistochemistry and molecular testing can be done. CT scans or ultrasounds are often used to guide the biopsy for lung cancer.

Fine needle aspiration (FNA) uses a very thin needle and syringe to remove a sample of cells, tissue or fluid from an abnormal area or lump in the body. It can be used to diagnose lung cancer. An FNA is used during an endoscopy to sample the lymph nodes in between the lungs. An FNA can also be used to take samples from a possible tumour that is found in the outer part of the lungs. The needle is inserted through the skin of the chest and is guided to the area during a CT scan so that tissue can be removed.

Core biopsy is like an FNA, except a larger needle or probe is used to remove tissue. Core biopsies can get larger amounts of tissue than an FNA, which helps with diagnosis and identifying the type of lung cancer.

Thoracentesis is a procedure that uses a needle to remove fluid from around the lungs. The fluid is examined to see if it has any cancer cells in it.

Surgical biopsy removes a piece of lung tissue so it can be examined. It is done through a cut (incision) made between the ribs.

Find out more about biopsy.


An endoscopy is done to remove tissue samples and to see how far lung cancer has spread. It allows a doctor to look inside the body using a flexible or rigid tube with a light and lens on the end. This tool is called an endoscope.

Bronchoscopy is used to look inside the large airways of the lungs (the trachea and bronchi) for a tumour or a blockage. Special bronchoscopes with an ultrasound sensor (endobronchial ultrasound or EBUS) allow biopsy of lymph nodes close to the trachea and bronchi for diagnosis or to find out if cancer has spread to the lymph nodes. Lymph nodes can also be sampled by ultrasound scopes inserted into the esophagus (EUS).

Mediastinoscopy is used to look at the area between the lungs called the mediastinum. Lymph nodes and other tissue samples near the trachea may be removed during a mediastinoscopy. Mediastinoscopy is only used if an EBUS is negative but the lymph nodes are still suspicious for cancer.

Thoracoscopy is used to look inside the chest cavity, including the chest wall, the lining of the lungs, and the lymph nodes in the chest. It may be done if other tests can’t get enough tissue for a diagnosis.

Find out more about bronchoscopy, mediastinoscopy and thoracoscopy.

Sputum tests

Mucus that is coughed up from the lungs (sputum) may be examined to see if it contains cancer cells. Several sputum samples are collected (usually in the early morning). If people have trouble coughing up sputum, they may be given a mist to inhale to help them cough.

Tumours in the large bronchi of the lung, squamous cell tumours and large tumours may shed cancer cells into the sputum.


Immunohistochemistry tests look for certain proteins (called antigens) that are found on the surface of cells. These tests can help identify the type and subtype of lung cancer.

Anaplastic lymphoma kinase (ALK) is a gene that controls the growth of cells. Immunohistochemistry staining can identify mutations in the ALK gene. ALK mutations in non–small cell lung cancer are more common in non-smokers or light smokers.

Another immunohistological test may be done to look for changes in the immune cells such as PD-L1.

The results of immunohistochemistry tests help doctors decide which treatment is the best option, based on the cancer that is identified.

Molecular tissue tests

Molecular tissue tests look for certain changes (mutations) in the genes of lung cancer cells. These changes affect the type of treatment given because some chemotherapy drugs may be more useful against cancer cells with these changes.

Molecular tissue tests for lung cancer look for certain gene changes.

Epidermal growth factor receptor (EGFR) is a protein found on the surface of cells that helps cells grow. Changes in the EGFR gene can cause a higher than normal amount of EGFR in some types of lung cancer. These changes are more common in non-smokers, women and people with Asian ancestry. This is the most common molecular tissue test used for lung cancer.

BRAF is a protein that sends signals in cells and helps with cell growth. Changes in the BRAF gene, called BRAF-V600E, can be found in higher amounts in some types of lung cancer.

ROS1 is another protein that sends signals in cells and helps with cell growth. Changes in the ROS1 gene can be found in higher than normal amounts in some types of lung cancer. These changes are more often seen in younger people or non-smokers and light smokers.

As newer targeted drugs are becoming available to treat lung cancer, testing for other mutations are being added to the molecular tissue tests for lung cancer.

Bone scan

A bone scan uses bone-seeking radioactive materials (called radiopharmaceuticals) and a computer to create a picture of the bones. It is done in people who have bone pain or if blood chemistry tests suggest that cancer has spread to the bones.

Find out more about bone scans.

Pulmonary function tests

Pulmonary function tests check how well the lungs are working. They measure how much air the lungs can hold and how well the person can let air out of the lungs. These tests are important if doctors are considering surgery as a treatment option for lung cancer. They help make sure that the person will have enough lung capacity after a lung or part of a lung is removed.

An arterial blood test may be done with pulmonary function tests. A small needle is used to remove blood from a small artery, usually on the back of the hand or on the wrist. The blood is tested for the levels of oxygen and carbon dioxide.

Questions to ask your healthcare team

Find out more about a diagnosis. To make the decisions that are right for you, ask your healthcare team questions about a diagnosis.


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