Lung cancer

You are here: 

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 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 usually 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 spread). 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 and risks 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
  • breathing in second-hand smoke
  • being around radon gas
  • being around asbestos at work

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 to see if your liver is larger than normal
  • check your blood pressure and pulse
  • check to see if you have lost any weight

Find out more about physical exams.

Complete blood count (CBC)

A complete blood count (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 (CBC).


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 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 3D 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
  • check if the tumour has spread 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 3D colour images of the area being scanned.

A PET scan is used to find out how far lung cancer has spread. It scans the whole body and can find tumours over 8 mm in size. It is more accurate than a 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 too much metabolic activity for the PET scan to be helpful.

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 3D pictures.

An MRI is used to look at the brain to see if lung 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 parts of the body. It is used to look for a buildup of fluid around the lungs and to guide a biopsy or removal of fluid in the chest cavity. An ultrasound is also used to guide a biopsy during endoscopic procedures.

Find out more about ultrasounds.

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 lung cancer has spread to the bones.

Find out more about bone scans.


During a biopsy, the doctor removes tissues or cells from the body so they can be tested in a lab. Getting enough tissue during a biopsy is important so that cell and tissue tests can be done. A report from a pathologist will show whether or not cancer cells are found in the sample.

A 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.

A core biopsy is like an FNA, except a larger needle 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.

A 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.

A 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. Different types of endoscopy are used to diagnose and stage lung cancer. They may be done as separate procedures, or they may be done during surgery for lung cancer.

A bronchoscopy is used to look inside the lungs 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.

A 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. A mediastinoscopy is only used if an EBUS is negative but the lymph nodes are still suspicious for cancer.

A 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 a bronchoscopy, mediastinoscopy and thoracoscopy.

Cell and tissue studies

Cells and tissues are analyzed in the lab to look for cancer. A report from a pathologist will show whether or not cancer cells are found in the sample, and what type of lung cancer has been found.

Molecular tissue tests look for certain changes (mutations) in the genes of lung cancer cells. These changes affect the type of treatment given. Specific targeted drugs are used for specific gene mutations. Molecular tissue tests for lung cancer look for the following 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. This is the most common molecular tissue test used for lung cancer.

Anaplastic lymphoma kinase (ALK) refers to a mutation in the anaplastic lymphoma kinase gene in the DNA. The gene controls a protein that helps with cell growth and division.

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.

ROS1is 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.

NTRK gene fusions are caused when a piece of the NTRK gene breaks off and joins with another gene. This change causes abnormal proteins called TRK fusion proteins, which may cause cancer cells to grow. TRK gene fusions are found in some types of lung cancer.

Cell and tissue tests are also used to look for markers on the cancer cells. Some cancer cells make too much of a certain protein that the immune system uses to tell the difference between normal and cancer cells. Specific immunotherapy drugs are used for specific immune system markers.

PD-L1 is a protein that helps control the body’s immune system response. It is often found in high amounts on cancer cells, including lung cancer cells. When it binds with another protein called PD-1, it stops the T cells in the immune system from killing the cancer cells.

As newer targeted and immunotherapy drugs are becoming available to treat lung cancer, testing for other targets are being added to cell and tissue studies.

Find out more about cell and tissue tests and genetic changes and cancer risk.

Blood chemistry tests

Blood chemistry tests measure certain chemicals in the blood. They show how well certain organs are working 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.

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 you have trouble coughing up sputum, you may be given a mist to inhale to help you cough.

Tumours in the in the large airway tubes of the lung (the main bronchi), squamous cell tumours and large tumours may shed cancer cells into the sputum.

Pulmonary function tests

Pulmonary function tests check how well your lungs are working. They measure how much air your lungs can hold and how well you can let air out of the lungs. These tests are important if your doctor is considering surgery as a treatment option for lung cancer. They help make sure that you 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 oxygen and carbon dioxide levels.

Find out more about pulmonary function tests.

Heart function tests

Heart function tests check how well your heart is working. These tests are important if your doctor is considering surgery as a treatment option for lung cancer. They will make sure that your heart is healthy enough for you to have and recover from surgery.

The heart function tests that you may have include:

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.


The chemical processes in the body that create and use energy. It includes breaking down food and transforming it into energy, eliminating wastes and toxins, breathing, circulating blood and regulating temperature.

Metabolic means referring to or having to do with metabolism, as in metabolic rate.


The study of disease, including causes, development and effects on the body.

The symptoms, processes or conditions of a disease.

A doctor who specializes in the causes and nature of disease is called a pathologist. Pathologists help determine diagnosis, prognosis and treatment by studying cells and tissues under a microscope and using laboratory tests.

Pathological means referring to or having to do with pathology. It can also refer to something related to or caused by a disease, as in pathological fracture.

squamous cell

A type of epithelial cell that is thin and flat and looks like a fish scale.

Squamous cells are found in the epithelium that makes up the surface of the skin. They are in the epithelium lining of organs such as the mouth, pharynx, esophagus, anus, cervix and vagina. Squamous cells also make up the lining of blood vessels and hollow areas of the body (called cavities).