Diagnosis of thymus cancer

Diagnosis is the process of finding out the cause of a health problem. Diagnosing cancer often means first ruling out other health conditions that share similar symptoms with cancer. It can be a very worrying time for you and your loved ones. Sometimes this process is quick. Sometimes it can feel long and frustrating. But it’s important for doctors to get all the information they need before making a diagnosis of cancer.

Usually, diagnosing thymus cancer begins when a test done for other reasons suggests a problem with the thymus. 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 thymus cancer or other health problems.

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.

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, pure 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 body and drooping eyelids
• check for signs of superior vena cava syndrome such as upper body swelling and problems breathing

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.

A chest x-ray is the imaging test often done to follow up on symptoms that suggest there is 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.

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 the main imaging test used to diagnose a thymus tumour because 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 or solid. A CT scan is also used to find out if a tumour has grown into nearby areas including lymph nodes, or spread to other areas of the body such as the liver, lungs, esophagus or heart.

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 may be used to find out if the tumour on the thymus is solid or a cyst.

Find out more about MRIs.

Blood tests measure certain cells or substances in the blood. They aren’t used to diagnose thymus cancer. But 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. Blood tests can also be done to help prepare for surgery or monitor response to treatment.

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 treatment starts.

Find out more about a complete blood count (CBC).

Blood chemistry tests measure certain chemicals in the blood. They show how well certain organs are working and can help find problems. They can also look for certain antibodies, or help diagnose an autoimmune disease and check hormone levels.

Find out more about blood chemistry tests.

Blood antibody tests may be used to diagnose myasthenia gravis. The antibodies that can be detected include:

• anti-acetylcholine receptor antibodies – about 85% of people with myasthenia gravis have high levels of this antibody in their blood
• muscle-specific tyrosine kinase (MuSK) antibodies – some people with the disease will have high levels of this antibody

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.

Thymomas are more commonly diagnosed with a CT scan. A biopsy is rarely done to diagnose a thymoma. If a biopsy is done, the tissue that was removed is examined for cancer cells after the tumour has been removed with surgery.

If your healthcare team suspects another, more aggressive type of tumour, such as a thymic carcinoma, a biopsy may be done to confirm the diagnosis.

A core biopsy (also called a core needle biopsy) uses a hollow needle to remove tissue from the body. 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.

A surgical biopsy is taken during surgery to remove the tumour. It may also be done if there wasn't enough tissue for a diagnosis removed during other biopsies. The following types of surgical biopsies may be used to diagnose thymic cancer.

• An anterior mediastinotomy (also called a Chamberlain procedure) is when an endoscope is inserted through a cut (incision) next to the breastbone.

• A mediastinoscopy is done to examine and biopsy the area in the chest with the thymus. A mediastinoscope (a type of endoscope) is placed through a small cut made at the base of the neck just above the breastbone. Find out more about a mediastinoscopy.

• A thoracoscopy is used to examine and do biopsies of the chest cavity. A thoracoscope (a type of endoscope) is inserted through a cut on the side of the chest between 2 ribs. Video-assisted thoracic surgery (VATS), which uses a thoracoscope with a small video camera attached to it, may be used. Find out more about a thoracoscopy.

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