Saint Luke’s Frank and Evangeline Thompson Thoracic Center provides expert diagnosis and treatment for thymic cancers and masses.

Thymus Cancer: Introduction

What is cancer?

Cancer is when cells in the body change and grow out of control. Your body is made up of tiny building blocks called cells. Normal cells grow when your body needs them, and die when your body does not need them any longer.

Cancer is made up of abnormal cells that grow even though your body doesn't need them. In most cancers, the abnormal cells grow to form a lump or mass called a tumor. If cancer cells are in the body long enough, they can grow into (invade) nearby areas. They can even spread to other parts of the body (metastasis).

What is thymus cancer?

Thymus cancer is cancer that starts in the thymus. This is a small organ in the front part of your chest under the breastbone. When your body is forming and growing during pregnancy and childhood, the thymus makes a type of white blood cell called a T-lymphocyte. These blood cells are important to your immune system. They grow in the thymus and then travel to the lymph nodes. This is where they help protect your body against infections. 

The thymus is lined by epithelial cells on its outer surface. These cells are where thymus tumors start. 

Types of thymus tumors

There are two main types of thymus tumors. Both of them are rare.


These are the more common type of tumor in the thymus. Most thymomas are slow growing, but they can be cancerous. They can also spread to other parts of your body. There are different types of thymomas. When your healthcare provider finds a thymoma, it’s classified based on two factors. These include how the cells look under a microscope and whether it’s spread past the thymus (and, if so, how far). Thymomas often show up with an autoimmune disease, such as myasthenia gravis.

Thymic carcinomas

These tumors also form from epithelial cells in the thymus, but they grow more quickly. They have often spread to other parts of your body by the time they are found.

There are other types of tumors that can start in the thymus, but these are very rare. These include carcinoids of the thymus.

Talk with your healthcare provider

If you have questions about thymus cancer, talk with your healthcare provider. He or she can help you understand more about this cancer.


Thymus Cancer: Diagnosis

If your healthcare provider thinks you might have a thymus tumor, you will need certain exams and tests to be sure. Diagnosing a thymus tumor starts with your healthcare provider asking you questions. He or she will ask you about your health history, your symptoms, risk factors, and family history of disease. Your healthcare provider will also give you a physical exam.

What tests might I need?

You may have one or more of the following tests:

  • Imaging tests

  • Blood tests

  • Biopsy

Imaging tests

Imaging tests are used to look for a thymus tumor.

Chest X-ray

If your healthcare provider thinks you have a problem in the middle of your chest, he or she may do an X-ray. It can often show tumors in the thymus, nearby organs, or lymph nodes.  

Computed tomography (CT) scan

For this test, you lie on a table as it slides through a CT scanner. The scanner takes many X-rays. Then a computer combines these images to make pictures for your healthcare provider to look at. CT scans show much more detail than chest X-rays.

Magnetic resonance imaging (MRI)

MRIs use radio waves and magnets to create very detailed images of the inside of your body. You may have this test if you cannot have a CT scan for some reason.

Positron emission tomography (PET) scan

For this test, you’re injected with a slightly radioactive sugar. Tumor cells collect more of the sugar than normal cells. Your healthcare provider then uses a special camera to take a picture of your whole body. The images from PET scans are not as detailed as those from CT or MRI scans. But they can often show if an abnormal area is a tumor. Some machines can do a PET scan and CT scan at the same time.

Blood tests

Blood tests cannot be used to diagnose thymus tumors. But they can still sometimes be helpful. For instance, your healthcare provider may do blood tests to look for antibodies in your blood. These can sometimes be found in people with myasthenia gravis or other autoimmune disorders linked to thymus tumors.


If your healthcare provider spots a thymus tumor on an imaging test, he or she will decide if it can be removed. If it can be, the next step is often surgery to remove the tumor and the thymus. In some cases, the diagnosis is not clear or surgery cannot remove the whole tumor. When this happens, your healthcare provider may remove a sample of the tumor during a biopsy. A doctor who specializes in looking at cells, called a pathologist, then looks at the samples under a microscope.

Needle biopsy

For this test, a thin, hollow needle is put through your skin and into the tumor to get a sample of it. This is often done during a CT scan of your chest. This lets your healthcare provider see the needle going into the tumor. This is less invasive than an open (surgical) biopsy. However, it may not always collect enough of a sample to make a clear diagnosis.

Open biopsy

A biopsy may be taken during surgery. This is more invasive than a needle biopsy. But it’s also more likely to provide a large enough sample for diagnosis.

Getting your test results

When your healthcare provider has the results of your tests, he or she will contact you with the results. Your provider will talk with you about other tests you may need if a thymus tumor is found. Make sure you understand the results and what follow-up you need.