Thymus Cancer Causes, Risk Factors, and Prevention

Learn about the risk factors for thymus cancer and if there are things you can do that might lower your risk.

What causes thymus cancer?

Not much is known about why thymus tumors (thymomas and thymic carcinomas) develop in some people but not in others. There are very few known risk factors for thymus cancer. These tumors don’t appear to have obvious inherited, environmental, or lifestyle-related causes.

How DNA and genes work

Cells are the basic building blocks of all living things, including our bodies. Genes control how cells function and are made up of DNA. Our DNA, which comes from both our parents, affects more than just how we look.

Gene changes and cancer

Different genes have different functions in our bodies. Certain genes help control when our cells grow, divide to make new cells, and help repair mistakes in DNA. Certain genes also cause cells to die when they’re supposed to. Learn more in Genes and Cancer.

If these genes aren’t working the way they should, it can lead to cells growing out of control. For example:

• Changes in genes that normally help cells grow, divide, or stay alive can lead to these genes being more active than they should be. This can cause them to become oncogenes. These genes can result in cells growing out of control.
• Genes that normally help keep cell division under control or cause cells to die at the right time are known as tumor suppressor genes. Changes that turn off these genes can result in cells growing out of control.
• Some genes normally help repair mistakes in a cell’s DNA. Changes that turn off these DNA repair genes can result in the buildup of DNA changes within a cell, which might lead to them growing out of control.

Any of these types of DNA changes might lead to cells growing out of control and forming a tumor. To learn more, see Oncogenes, Tumor Suppressor Genes, and DNA Repair Genes.

Inherited versus acquired gene mutations

People have 2 copies of each gene in their cells. One copy comes from each parent.

Some people inherit DNA changes (mutations) from a parent that increase their risk of some types of cancer. But inherited gene mutations do not seem to play a role in thymus cancers.

In many cancers, the gene changes inside the cancer cells are acquired during a person’s life. Thymus cancers (especially thymomas) tend to have very few gene mutations compared to many other types of cancer. Genes that are sometimes mutated in thymoma cells include GTF2I, TP53, KIT, and CDKN2A.

Of these, GTF2I mutations are the most common. This gene change is found in 75% to 85% of type A and AB thymomas. Tumors with GTF2I mutations tend to be less aggressive and have a better outlook than those without this mutation. KIT mutations are more commonly found in thymic carcinoma than in thymoma. Knowing what type of gene change is involved may help the care team make treatment decisions.

It’s not clear if there are any outside factors that cause these gene changes. Sometimes they may just be random events that happen inside a cell when it divides to make two cells, without having another cause.

What is a risk factor?

A risk factor is anything that increases your chances of getting a disease such as cancer. Different cancers have different risk factors. For example, exposing the skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for lung cancer and many others.

But having a known risk factor, or even several risk factors, does not mean that you will get the disease. And many people who get the disease may have few or no known risk factors.

What are the risk factors for thymus cancer?

No specific inherited, environmental, or lifestyle risk factors have been strongly linked to thymoma or thymic carcinoma. Some studies have suggested a possible link with radiation exposure to the upper chest area, but this has not been confirmed.

Thymus cancer is rare, so it isn’t easy to study. Still, the only known risk factors are age and ethnicity. Autoimmune conditions are often related to thymomas.

Can thymus cancer be prevented?

There are very few known risk factors for thymus cancer, and none of these factors can be changed. Because of this, there is currently no known way to prevent it.