Thymoma & Thymic Cancer, from the CureRays guide library.

These rare tumors of the thymus gland behind the breastbone are often slow-growing and very treatable; surgery is the cornerstone, and radiation helps secure control after surgery or when removal isn't complete.

What it is.

Thymoma and thymic carcinoma are rare tumors that grow in the thymus, a small gland that sits behind the breastbone in the front of the chest, between the lungs. The thymus is part of the immune system and is most active early in life, helping train the body's T-cells. Tumors that arise there are uncommon and span a wide range of behavior: most thymomas grow slowly and are relatively contained, while thymic carcinoma is less common and more aggressive. A distinctive feature is that thymomas are often associated with autoimmune conditions — most notably myasthenia gravis, a disorder of muscle weakness — and sometimes a tumor is discovered while doctors investigate one of these conditions. Many are found by chance on a chest scan done for another reason. Surgery to remove the tumor is the foundation of treatment, and radiation and chemotherapy play important supporting roles depending on the tumor's extent and type.

How radiation treats it.

Radiation uses focused high-energy x-rays to damage the DNA of tumor cells so they can no longer grow and divide. Thymic tumors sit in the middle of the chest, surrounded by the heart, lungs, great vessels, and spinal cord, so precision is essential — and it is exactly where modern radiation excels. After surgery, radiation aimed at the area where the tumor was can lower the chance it returns, especially when the tumor had grown into nearby tissue or could not be completely removed. When surgery isn't possible, radiation — often combined with chemotherapy — can control the tumor directly. Advanced techniques such as intensity-modulated radiation, image guidance, and in some centers proton therapy let the team shape the dose tightly around the target while sparing the heart and lungs, which matters greatly for long-term health. Treatments are painless and brief, given over a number of sessions. Side effects depend on the area treated and are usually temporary, such as fatigue, mild swallowing discomfort, or skin irritation.

The ways we can treat it.

Post-operative (adjuvant) radiation. Precisely targeted radiation to the tumor bed after surgery lowers the chance of the tumor returning, particularly when it had invaded nearby tissue or wasn't fully removed.

Definitive radiation. For tumors that can't be safely operated on, radiation — often with chemotherapy — is used to control the tumor, shaped carefully to protect the heart, lungs, and spinal cord nearby.

Advanced, organ-sparing techniques. Modern image-guided and intensity-modulated radiation, and in some centers proton therapy, concentrate the dose on the tumor while sparing the heart and lungs, reducing long-term effects.

Questions we hear often.

What is the thymus, and why did I get a tumor there? The thymus is a small immune gland behind the breastbone, most active in childhood. Tumors there are rare and usually develop without a clear cause. Sometimes they're found by chance on a scan, and sometimes they come to light while doctors investigate an autoimmune condition such as myasthenia gravis, which can accompany thymoma.

Will I need radiation after surgery? It depends on the tumor. A small thymoma fully contained within its capsule and completely removed often needs no further treatment. If the tumor had grown into nearby tissue or couldn't be entirely removed, radiation afterward lowers the chance it returns. Your team will base the recommendation on the surgery findings and tumor type.

Are these tumors curable? Many are, especially thymomas that are contained and fully removed by surgery — cure rates are high. More invasive tumors and thymic carcinoma are more challenging but are still very treatable with a combination of surgery, radiation, and chemotherapy, and many people do well for years.

This guide is informational only. It is not medical advice — please confirm anything here with your care team.