Thymoma and thymic carcinoma are diseases in which malignant (cancer) cells form on the outside surface of the thymus.
The thymus, a small organ that lies in the upper chest under the breastbone, is part of the lymph system. It makes white blood cells, called lymphocytes, that protect the body against infections.
Anatomy of the thymus gland. The thymus gland is a small organ that lies in the upper chest under the breastbone. It makes white blood cells, called lymphocytes, which protect the body against infections.
There are different types of tumors of the thymus. Thymomas and thymic carcinomas are rare tumors of the cells that are on the outside surface of the thymus. The tumor cells in a thymoma look similar to the normal cells of the thymus, grow slowly, and rarely spread beyond the thymus. On the other hand, the tumor cells in a thymic carcinoma look very different from the normal cells of the thymus, grow more quickly, and have usually spread to other parts of the body when the cancer is found. Thymic carcinoma is more difficult to treat than thymoma.
For information on thymoma and thymic carcinoma in children, see the PDQ summary on Unusual Cancers of Childhood.
Thymoma is linked with myasthenia gravis and other autoimmune diseases.
People with thymoma often have autoimmune diseases as well. These diseases cause the immune system to attack healthy tissue and organs. They include:
- Myasthenia gravis.
- Acquired pure red cell aplasia.
- Lupus erythematosus.
- Rheumatoid arthritis.
- Sjögren syndrome.
Possible signs of thymoma and thymic carcinoma include a cough and chest pain.
Sometimes thymoma and thymic carcinoma do not cause symptoms. The cancer may be found during a routine chest x-ray. The following symptoms may be caused by thymoma, thymic carcinoma, or other conditions. Check with your doctor if you have any of the following problems:
Tests that examine the thymus are used to detect (find) thymoma or thymic carcinoma.
The following tests and procedures may be used:
- Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient's health habits and past illnesses and treatments will also be taken.
- Chest x-ray: An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
- CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, such as the chest, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
- MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body, such as the chest. This procedure is also called nuclear magnetic resonance imaging (NMRI).
- PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.