Thymic Cancer

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 starts when cells in the body change (mutate) 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 doesn't 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 a rare cancer that starts in the cells that make up the thymus. The thymus is a small organ in the front part of your chest under the breastbone (sternum) and in front of and above the heart. The thymus has two lobes.

When your body is forming and growing during infancy and childhood, the thymus makes a type of white blood cell called a T-lymphocyte (T cell). These blood cells are a key part of 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 becomes smaller in adulthood as it's replaced by fat.

The thymus is covered 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 are quite rare. These both start from thymic epithelial cells but act very differently.

Thymomas

These are the more common type of tumor in the thymus. Most thymomas are slow-growing cancers. In rare cases, they can spread to other parts of the body.

There are different types of thymomas. When your healthcare provider finds a thymoma, it’s classified based on two factors: how the cells look under a microscope and whether the tumor has spread past the thymus (and, if so, how far). Thymomas are often linked to autoimmune diseases, like myasthenia gravis and Good syndrome.

Thymic carcinomas

These tumors also form from epithelial cells in the thymus, but they grow faster. They've often spread to other parts of the body by the time they are found. They can be harder to treat.

Other types

There are other types of tumors that can start in the thymus, but these are very rare. These include lymphoma, carcinoid, and germ cell tumors of the thymus.

Talk with your healthcare provider

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

Diagnosis

Thymus Cancer: Diagnosis

If your healthcare provider thinks you might have a thymus tumor, you'll need some exams and tests to make sure. The process starts with your healthcare provider asking you questions. You'll be asked about your health history, your symptoms, risk factors, and family history of disease. They will also give you a physical exam.

Based on your answers and the exam, your provider will decide what tests you may need. Your provider may also consider the type of cancer suspected, your age, and general health.

What tests might I need?

You might need 1 or more of these kinds of tests:

  • Imaging tests

  • Blood tests

  • Biopsy

Imaging tests

Imaging tests can be 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, an X-ray may be the first test done. If anything is abnormal, you will need additional imaging.

CT scan

For this test, you lie on a table as it slides through a ring-shaped CT scanner. The scanner uses X-rays to take pictures from many angles. Then a computer combines these images to make 3-D pictures of your insides. A CT scan shows much more detail and picks up soft tissue tumors that X-rays can't. You may be given a contrast dye (contrast medium) to drink. Or contrast may be given by IV (intravenous) line through a vein in your hand or arm. The contrast will help make the pictures clearer.

MRI

An MRI uses radio waves and powerful magnets instead of X-rays to create very detailed images of the inside of your body. You may have this test if you can't have a CT scan for some reason. MRI is also very good at showing if cancer has spread to the brain or spinal cord. A contrast medium is often given by IV through a vein in your hand or arm to make the images clearer.

PET (positron emission tomography) scan

For this test, you’re injected with a small amount of radioactive sugar. Cancer cells collect more of the sugar than normal cells. After about 1 hour, a special camera is used to take a picture of your whole body. It shows where the radioactive sugar has collected. These spots might be cancer.

The images from PET scans are not as detailed as those from CT scans. Some machines can do a PET scan and CT scan at the same time. This test is useful if your healthcare provider thinks the cancer may have spread but isn't sure where.

Blood tests

Blood tests aren't used to diagnose thymus tumors. But they can sometimes help rule out other problems and get a general idea of your overall health. For instance, your healthcare provider may do blood tests to look for antibodies in your blood. Certain antibodies can sometimes be found in people with myasthenia gravis or other autoimmune disorders linked to thymus tumors.

Biopsy

A biopsy is a procedure to remove tiny pieces (samples) of tissue to look for cancer cells. If your healthcare provider sees a thymus tumor on an imaging test, they will decide if it can be removed. If it can be, the next step is often surgery to take out the whole tumor.

In some cases, the diagnosis isn't clear on the imaging tests, or the whole tumor can't be removed. When this happens, you may have a biopsy instead. A doctor who specializes in looking at cells, called a pathologist, then looks at the samples. They do tests to see if there are cancer cells in the samples.

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 allows your healthcare provider to watch the needle go into the tumor and make sure the sample is taken from the right place. Sometimes a needle biopsy doesn't get enough tissue to make a clear diagnosis.

Open biopsy

Surgery can be done for a biopsy. A 2-inch cut is made next to the breastbone (sternum) so a piece of the tumor can be removed. This is more involved than a needle biopsy. But it’s also more likely to provide a large enough sample for diagnosis.

Getting your test results

It often takes a few days for your biopsy results to come back. When your healthcare provider has the results, they will contact you. Ask how you can expect to find out your biopsy results. Will it be a phone call, or do you need to make an appointment?

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 your next steps should be.