What is a thymoma?
Thymoma is a tumor of the thymus gland which is located in the chest behind the breast bone. In children, the thymus gland produces immune cells, but in adulthood the thymus gland no longer serves an important function. Thymomas can be slow growing or can be more aggressive and spread in the blood stream. Thymic carcinomas are the most aggressive tumors of the thymus gland.
How is a thymoma diagnosed?
Thymomas may cause symptoms or be found by chance on chest X-rays or CT scans done for other reasons. Thymomas are associated with myasthenia gravis, an autoimmune disease causing muscle weakness. Very large thymomas may also cause symptoms such as cough and shortness of breath. If the thymoma appears small, your surgeon may recommend surgical removal without a biopsy. However, if the tumor is large or if the diagnosis of thymoma is not certain, your surgeon may recommend that you undergo a CT-guided core needle biopsy, which is done in radiology.
Stages of Thymoma (Masaoka staging)
  • Stage I: The tumor is contained within the thymus gland
  • Stage II: The tumor invades through the “capsule” of the thymus gland into the surrounding fatty tissue
  • Stage III: The tumor invades into neighboring organs in the chest (such as the lung)
  • Stage IVa: Spread of the tumor into the chest lining or heart sack lining
  • Stage IVb: Spread of the tumor to lymph nodes or to other organs through the blood stream

Treatment of Thymoma
Surgical removal of thymoma is the mainstay of treatment for thymomas that can be completely removed. Patients with stage III and IVa thymoma typically receive chemotherapy prior to surgery, and may receive radiation therapy after surgery. Some patients with stage II thymoma will be recommended to undergo radiation therapy after surgery. At City of Hope, we offer the following types of surgery for thymoma.
Minimally Invasive Robotic Thymectomy
The thymoma and entire thymus gland are removed through small incisions in the side of the chest. Most patients with stage I and some with stage II thymoma are eligible for this treatment, depending on the size of the tumor. Most patients are able to be discharged from the hospital the day after surgery.
Thymectomy through sternotomy
This more traditional approach involves dividing the breast bone down the middle of the chest. This is often necessary for large tumors or stage III and IVa tumors invading neighboring organs in the chest.
Thymectomy for IVa and Recurrent Thymoma
Surgical removal of the chest wall lining and thymoma that has recurred can be successfully accomplished.
Clinical Trials
City of Hope is one of a handful of medical centers in the United States with active clinical trials in patients with thymomas. Contact us to learn more.