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A thymoma is a tumor that originates in the thymus, a small gland located in the upper chest behind the breastbone. As part of the lymphatic system, the thymus produces and trains certain white blood cells (T-cells) to help the immune system fight off infections. Additionally, as part of the endocrine system, the thymus produces and releases certain hormones that regulate the body’s immune response and other functions. The thymus is most active during childhood; after puberty, it gradually decreases in size and is replaced by fat.

Thymoma is relatively uncommon, accounting for only about 1% of adult cancers. It is usually diagnosed between the ages of 40 and 60.

Early warning signs of thymoma

Thymoma tends to be slow-growing and rarely spreads beyond the thymus. Most early-stage tumors do not produce noticeable symptoms. Instead, they are usually discovered incidentally during an imaging test performed for an unrelated reason.

In many cases, the first warning sign of a thymoma is persistent coughing.

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Common symptoms of thymoma

Due to the location of the thymus in the upper chest near the lungs, thymoma symptoms often affect the respiratory system.

What does thymoma feel like?

Most thymomas do not cause physical sensations. However, if a thymoma grows large enough to press on a nearby structure, such as the windpipe (trachea) or lungs, it may cause symptoms that can be felt, such as:

  • Dry coughing
  • Dull or aching pain in the chest
  • Difficulty breathing
  • Shortness of breath
  • A sensation of pressure or fullness in the chest
  • Difficulty swallowing

What does thymoma look like?

In medical images such as chest X-rays, computerized tomography (CT) scans and magnetic resonance imaging (MRI) scans, a thymoma may appear as a well-defined mass in the front part of the chest between the lungs, an area known as the anterior mediastinum. The tumors can vary in size and appearance, ranging from small and localized to large and invasive.

Additionally, a growing thymoma may cause visible swelling in the face, neck and upper chest.

Can thymoma cause an autoimmune disorder?

Thymoma can interfere with the thymus’ production of normal antibodies, which may lead to an autoimmune disorder. For instance, myasthenia gravis may develop if the thymus produces abnormal antibodies that destroy the communication link between nerves and muscles, leading to muscle weakness and fatigue.

Other autoimmune disorders that may be related to thymoma include:

  • Pure red cell aplasia – A rare blood disorder that occurs when the bone marrow does not produce enough healthy red blood cells, which can lead to anemia
  • Hypogammaglobulinemia – An immune system disorder caused by low levels of certain antibodies (immunoglobulins) in the blood, which can increase susceptibility to infection

Are frequent infections a symptom of thymoma?

Because thymoma affects the thymus, the cancer can weaken the immune system and impair its ability to fight off infections. However, recurrent infections can have many causes other than cancer, such as allergies, asthma, diabetes and poor nutrition. Usually, imaging studies and lab tests are needed to help a physician determine if the infections are related to thymoma.

Symptoms of an advanced thymoma

The signs of a late-stage thymoma can vary depending on the size and location of the tumor and whether cancerous cells have spread to other parts of the body. In general, as the cancer progresses, it may deplete the body’s energy reserves, leading to:

  • Fatigue
  • Weakness
  • Dizziness
  • Unintended weight loss

Benefit from world-class care at Moffitt Cancer Center

Moffitt is a high-volume cancer center, and the multispecialty team in our Thymoma Program is well-versed in the warning signs of thymoma, an exceedingly rare type of cancer. With access to the latest diagnostic techniques and technologies, we can quickly evaluate thymoma symptoms and accurately diagnose the underlying cause. After confirming a diagnosis of thymoma or another type of thoracic cancer, we can develop an individualized treatment plan to address it.

If you would like to learn more about thymoma signs and symptoms, you can request an appointment with a specialist in Moffitt's Thymoma Program by calling 1-888-663-3488  or submitting a new patient registration form online. We do not require referrals.