The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on September 21, 2021.


Thymoma is a type of tumor that occurs in the thymus gland, a small organ in the upper chest that makes up part of the lymphatic system. The thymus produces white blood cells, which are used by the body to fight off infection.

Thymoma is one of two types of thymic epithelial tumors, the other being thymic carcinoma. Both are rare cancers, although each behaves differently. Thymomas are more slow-growing, while thymic carcinomas tend to grow faster and spread.

Thymomas are diagnosed in about 400 people every year, according to the American Society of Clinical Oncology.


Sometimes, thymomas may not show symptoms. However, the most common symptoms include:

  • Shortness of breath
  • Persistent cough
  • Pain in the chest
  • Double vision
  • Swelling in the face or arm
  • Eyelids that droop Fatigue
  • Dizziness

Anyone experiencing such symptoms should see a doctor. Even though the symptoms may be caused by different conditions, it’s best to have a physical examination to rule out any health issues.

Causes and risk factors

There are no known causes or risk factors for thymomas. But there seems to be a relationship between thymic cancers and a few autoimmune paraneoplastic disorders, particularly myasthenia gravis (MG). About 30 to 65 percent of patients with thymomas have MG as well, though not all people with MG have thymomas, according to the American Cancer Society.

Thymoma is linked to other autoimmune diseases as well, including good syndrome (GS) and pure red cell aplasia (PRCA).

In the United States, thymic cancers tend to be more common in people of Asian and Pacific Islander heritage. They’re also more likely to develop with advancing age.

How is thymoma diagnosed?

If thymoma is suspected, doctors may conduct a physical examination and review the patient’s medical history, taking into account symptoms, age and pre-existing health conditions.

There are also a number of diagnostic tools that allow doctors to look for thymoma within internal areas of the body. These include:

If the scans reveal abnormal results, a biopsy may be performed, which allows the doctor to definitively diagnose a tumor as cancerous. A biopsy may be done with a needle or surgically. The surgical biopsy, known as a Chamberlain procedure, involves making a cut near the breastbone and removing part of the tumor for a pathologist to examine.

If it’s clear from the imaging tests that a thymoma is present, doctors may skip the biopsy process and go straight to removing the tumor.

During a diagnosis, the doctor may share the stage of cancer, which describes the disease’s growth and spread. This detail is necessary, as it guides treatment options. Thymic tumors are also assigned a classification type, based on the pattern of cells within the tumor.

A diagnosis of thymoma may be unexpected and frightening, so patients should ask their care team plenty of questions to better understand the disease and next steps.

How is thymoma treated?

Doctors may recommend the most appropriate course of treatment based on the tumor’s stage, classification, and whether or not it’s spread to other parts of the body.

The most common thymoma treatment is surgery. Usually, this is a procedure called a median sternotomy, in which the breastbone is opened and the thymoma and surrounding tissue are removed. For smaller thymomas, the surgery may be done laparoscopically.

Other commonly used treatments include:

  • Radiation: Using high-energy X-ray beams directed at the tumor, cancer cells are destroyed.
  • Chemotherapy: A drug, or combination of drugs, is taken to kill cancer cells. Chemotherapy is used as a standalone treatment or before surgery to help shrink the tumor.
  • Targeted therapy: Doctors tailor treatment based on the properties of the tumor, such as its genes or proteins.

It’s important to remember that all thymoma treatments may potentially lead to side effects, which may be uncomfortable. Doctors may help answer any questions about what to expect after treatment and how to reduce discomfort and side effects.

In fact, doctors are always the best source of information when it comes to managing thymoma or other cancers.

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