Diagnosis of thymus cancer

Diagnosis is the process of finding out the cause of a health problem. Diagnosing thymus cancer may begin with a visit to your family doctor. Your doctor will ask you about any symptoms you have and may do a physical exam. But most often thymus cancer is found by chance when you have tests for other reasons.

Based on this information, your doctor may refer you to a specialist or order tests to check for thymus 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 to thymus cancer. It’s important for the healthcare team to rule out other reasons for a health problem before making a diagnosis of thymus cancer.

The following tests are usually used to rule out or diagnose thymus 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, 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 thymus cancer
  • symptoms that suggest a paraneoplastic syndrome such as myasthenia gravis, red cell aplasia or hypogammaglobulinemia
  • autoimmune diseases

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

  • feel the lower neck to check for swelling or a feeling of fullness
  • check for signs of myasthenia gravis such as muscle weakness in the face and neck
  • check for signs of superior vena cava syndrome

Find out more about physical exams.


An x-ray uses small doses of radiation to make an image of parts of the body on film. It is often the first imaging test done to check for a tumour in the front mediastinum or other parts of the chest. An x-ray is also used to measure the size of a tumour and check its exact location.

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 get a closer look at the chest. It can find small tumours in the mediastinum better than a chest x-ray. It is used to check if the tumour is filled with fluid (a cyst) or solid. A CT scan is also used to find out if a tumour has grown into nearby areas or spread to other areas of the body, such as nearby lymph nodes or the liver.

Find out more about CT 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 of the chest may be used to look more closely at a thymus tumour and check if it’s a cyst. It may also be used to find out if thymus cancer has grown into other areas of the body, such as the spinal cord.

Find out more about MRIs.

PET-CT 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-CT scan combines a PET scan and a CT scan so they are done at the same time using the same machine. It may be used to help stage thymus cancer and check if it has spread to lymph nodes or other parts of the body. Doctors may also use a PET-CT scan to check how well cancer treatment is working. A PET-CT scan for thymus cancer may not be used in all parts of Canada.

Find out more about PET scans.

Blood tests

Blood tests measure certain cells or substances in the blood. They can provide helpful information about your general health, how some organs are working and if a tumour is releasing certain substances into the blood. They can also be done to help prepare for surgery or monitor response to treatment.

Blood tests that may be done include:


During a biopsy, the doctor removes tissues or cells from the body so they can be tested in a lab. A report from the pathologist will show whether or not cancer cells are found in the sample.

Depending on where the tumour is, one of the following procedures may be used:

Core biopsy

A core biopsy (also called a core needle biopsy) uses a hollow needle to remove tissue from the body. It is the most common type of biopsy used to diagnose tumours in the mediastinum. An imaging test, such as a CT scan, is usually used to guide the needle through the chest wall into the tumour. A thin needle may be used instead, but it may not be able to remove enough tissue for diagnosis.

Find out more about a core biopsy.

Chamberlain procedure (also called anterior mediastinotomy) is a surgical procedure where an endoscope is inserted through a cut (incision) next to the breastbone. It is the most common type of biopsy done to diagnose thymus cancer.

Mediastinoscopy is a surgical procedure that lets the doctor examine the mediastinum and take biopsies from it. An endoscope (called a mediastinoscope) is placed through a small cut made at the base of the neck just above the breastbone.

Find out more about a mediastinoscopy.

Thoracoscopy is a surgical procedure to examine and get biopsies from the chest cavity. An endoscope (called a thoracoscope) is inserted through a cut on the side of the chest between 2 ribs. Video-assisted thoracic surgery (VATS) may be done, which uses a thoracoscope with a small video camera attached to it.

Find out more about a thoracoscopy.

Surgical biopsy

Sometimes a biopsy is taken during surgery to diagnose thymus cancer. A surgical biopsy is used if the doctor can’t remove enough tissue using another type of biopsy.

Find out more about a surgical biopsy.

Questions to ask your healthcare team

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

Expert review and references

Medical disclaimer

The information that the Canadian Cancer Society provides does not replace your relationship with your doctor. The information is for your general use, so be sure to talk to a qualified healthcare professional before making medical decisions or if you have questions about your health.

We do our best to make sure that the information we provide is accurate and reliable but cannot guarantee that it is error-free or complete.

The Canadian Cancer Society is not responsible for the quality of the information or services provided by other organizations and mentioned on cancer.ca, nor do we endorse any service, product, treatment or therapy.

1-888-939-3333 | cancer.ca | © 2024 Canadian Cancer Society