Facts About Thymus Cancer

April 11, 2026

This page was reviewed under our medical and editorial policy by Amanda Reyes, M.D., Medical Oncologist, City of Hope^® Cancer Center Duarte. 

Thymus cancer is the term for any type of cancer that develops in the thymus gland. Found in the upper part of the chest, the thymus gland plays a crucial role in producing some of the body’s immune cells. Thymus cancers are rare and may affect several different types of cells.

What Is Thymus Cancer?

Thymus cancer is the result of cells growing abnormally and forming a mass called a tumor in or on the thymus gland — a small, irregularly shaped gland located in the upper abdomen, just behind the breastbone. The thymus helps create T cells, a type of immune system cell.

Although rare, there are several different kinds of thymus cancer, named for the type of cell they develop in, as listed below.

Thymic epithelial tumors (TETs): Sometimes referred to as thymoma or thymic carcinoma, TETs are tumors that start in the epithelial cells, which are the cells that give the thymus its shape. These are by far the most common type of thymus cancer. 

Thymic neuroendocrine tumors (TNETs): These are very rare, developing in the neuroendocrine cells — which are cells that acts as a bridge between the body’s nervous system and hormone-producing system

How Common Is Thymus Cancer?

Thymus cancers are rare, with only around 400 new cases diagnosed each year in the United States.

What Causes Thymus Cancer?

At a basic level, all cancers are caused by gene mutations that lead to abnormal cell behavior. However, doctors do not fully understand why some people develop thymus cancers while others do not.

Because thymus cancer is so rare, scientists do not have a lot of data about risk factors related to developing the disease. The only known risk factors for developing thymus cancer are:

• Being middle-aged or older
• Being an Asian American, a Native Hawaiian or a Pacific Islander
• Having prior exposure to radiation, especially to the chest wall in childhood

Is Thymus Cancer Genetic?

Thymus cancer is not typically associated with known inherited genetic syndromes outside of rare cases. One exception would be very rare thymic neuroendocrine tumors, which are associated with multiple endocrine neoplasia-1 (MEN-1).

How to Detect Thymus Cancer

If doctors suspect that a patient has thymus cancer, they first perform a physical examination and have a discussion with their patient about any symptoms they may be experiencing. They may also recommend other tests to help diagnose thymus cancer, including:

• Imaging tests, such as magnetic resonance imaging, computed tomography/positron emission tomography or X-ray, which may detect a tumor’s size and location
• Biopsy, which is a medical procedure to remove a tissue sample from the site of a tumor for examination in a lab for signs of cancer
• Blood tests, which may help detect changes to how the immune system or hormone-producing systems are working