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Tests for Thymus Cancer

If there is a reason to think you might have a thymus tumor (such as a thymoma or thymic carcinoma), your doctor will ask you about symptoms and use one or more exams or tests to check for one. Certain signs and symptoms might suggest that a person has a thymus tumor, but tests are needed to know for sure.

Medical history and physical exam

If you have signs or symptoms that suggest you might have a thymus tumor, your doctor will want to take a complete medical history to learn more about your symptoms. You will also be asked about your general health.

A physical exam provides information about possible signs of thymic tumors and other health problems. People with thymic tumors will sometimes have a fullness that the doctor can feel in the lower neck area.

Thymomas are often suspected if you have signs and symptoms linked with myasthenia gravis, hypogammaglobulinemia, or red cell aplasia. (See Signs and Symptoms of Thymus Cancers for more on these conditions.)

Imaging tests

Imaging tests use x-rays, magnetic fields, or radioactive substances to create pictures of the inside of your body. Imaging tests may be done for a number of reasons, including:

  • To help find a suspicious area that might be cancer
  • To learn how far cancer may have spread
  • To help see if treatment is working
  • To look for signs that cancer has come back

Chest x-ray

A chest x-ray may be the first imaging test a doctor orders if they suspect a problem in the middle of the chest. It may be able to show if there is a tumor in the chest. In some cases, a chest x-ray may find a tumor when a person is having the test done for another reason. But some thymomas are small or in places that may not show up on a chest x-ray. If your doctor is still suspicious or if a change is seen on the chest x-ray, a CT scan may be ordered.

Computed tomography (CT) scan

A CT scan uses x-rays to make detailed, cross-sectional images of your body. Unlike a regular x-ray, a CT scan creates detailed images of the soft tissues in the body. A chest CT is often done using an IV contrast (where a special dye is put into a person's blood before the test to help make any tumors stand out more on the images).

CT scans can also be used to help guide a biopsy needle precisely into a suspected tumor or metastasis. This is called a CT-guided needle biopsy.

Magnetic resonance imaging (MRI) scan

Like CT scans, MRI scans provide detailed images of soft tissues in the body. But MRI scans use radio waves and strong magnets instead of x-rays.

MRI of the chest may be done to look more closely at thymus tumors. This test is most often used for people who cannot have a CT scan for medical reasons (like problems with the IV contrast). MRI images are also particularly useful in looking for cancer that may have spread to the brain or spinal cord.

Positron emission tomography (PET) scan

For a PET scan, you are injected with a slightly radioactive form of sugar, which collects mainly in cancer cells. A special camera is then used to create a picture of areas of radioactivity in the body. The picture is not detailed like a CT or MRI scan, but a PET scan can look for possible areas of cancer spread in all areas of the body at once.

A PET scan can help give the doctor a better idea of whether a change seen on another imaging test is a tumor or not. If you have already been diagnosed with cancer, your doctor may use this test to see if the cancer has spread to lymph nodes or other parts of the body. A PET scan can also be useful if your doctor thinks the cancer may have spread but doesn’t know where.

Certain machines are able to perform both a PET and CT scan at the same time (PET/CT scan). This lets the doctor compare areas of higher radioactivity on the PET scan with the more detailed pictures of that area on the CT. Combined PET/CT is used more often than a PET scan alone when looking at thymomas.

Blood tests

Blood tests can’t be used to diagnose thymomas, but they may be helpful in some situations. For example, blood tests may be done:

  • To look for certain antibodies if myasthenia gravis (MG) or another autoimmune disorder is suspected
  • To make sure a mass in the middle of the chest isn’t a germ cell tumor or part of the thyroid gland

If a thymoma is diagnosed, blood cell counts and blood chemistry tests are done to get an idea of a person’s overall health, especially if surgery is planned. Also, tests for myasthenia gravis will be done before any surgery. This is because MG is very common in people with a thymoma, and, if not treated, it can cause problems with the drugs used during surgery. People getting chemotherapy need regular blood tests to make sure the drugs aren’t having unwanted effects on the bone marrow, kidneys, or other organs.


Although signs, symptoms, and imaging tests can suggest that a thymic tumor is likely, doctors can’t be certain of the diagnosis without looking at the tumor under a microscope.

For most cancers, taking out a small piece of the tumor (known as a biopsy) is needed to confirm whether a tumor is present and, if so, to determine its type. For thymomas, this isn't often done because doctors can usually tell that the tumor is very likely a thymoma based on how it looks on imaging tests. Because of this, doctors often remove the entire tumor during surgery, rather than do a biopsy. This provides tissue for a diagnosis and treats the tumor at the same time. The specimen is sent to the lab after surgery to confirm the diagnosis.

If the tumor can't be removed completely during surgery, a biopsy might be done to confirm the diagnosis. This might be done with a long, hollow needle (a core needle biopsy) or during surgery (an open biopsy). This helps the doctor decide if more treatment is needed after surgery.

If the doctor suspects a different type of tumor, a biopsy (usually a needle biopsy) might be done before surgery.

See Testing Biopsy and Cytology Specimens for Cancer to learn more about types of biopsies, how the tissue is used in the lab to diagnose cancer, and what the results may show.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.

Meneshian A, Oliver KR, Molina JR. Clinical presentation and management of thymoma and thymic carcinoma. UpToDate. 2024. Accessed at on May 14, 2024.

National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines: Thymomas and Thymic Carcinomas. Version 1.2024. Accessed at on May 14, 2024.

Last Revised: May 15, 2024

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