General Information About Thymoma and Thymic Carcinoma

Thymoma and thymic carcinoma are diseases in which malignant (cancer) cells form in the thymus.

Thymoma and thymic carcinoma, also called thymic epithelial tumors (TETs), are two types of rare cancers that can form in the cells that cover the outside surface of the thymus. The thymus is a small organ that lies in the upper chest above the heart and under the breastbone. It is part of the lymph system and makes white blood cells, called lymphocytes, that help fight infection. These cancers usually form between the lungs in the front part of the chest and are sometimes found during a chest x-ray that is done for another reason.

Even though thymoma and thymic carcinoma form in the same type of cell, they act differently:

• Thymoma. The cancer cells look a lot like the normal cells of the thymus, grow slowly, and rarely spread beyond the thymus.
• Thymic carcinoma. The cancer cells do not look like the normal cells of the thymus, grow more quickly, and are more likely to spread to other parts of the body. About one in every five TETs is a thymic carcinoma. Thymic carcinoma is more difficult to treat than thymoma.

Other types of tumors, such as lymphoma or germ cell tumors, may form in the thymus, but they are not considered to be thymoma or thymic carcinoma.

Thymoma is linked with myasthenia gravis and other autoimmune paraneoplastic diseases.

Autoimmune paraneoplastic diseases are often linked with thymoma. Autoimmune paraneoplastic diseases may occur in patients with cancer but are not caused directly by cancer. Autoimmune paraneoplastic diseases are marked by signs and symptoms that develop when the body's immune system attacks not only cancer cells but also normal cells. Autoimmune paraneoplastic diseases linked with thymoma include:

• Myasthenia gravis (the most common autoimmune paraneoplastic disease linked with thymoma).
• Thymoma-associated hypogammaglobulinemia (Good syndrome).
• Thymoma-associated autoimmune pure red cell aplasia.

Other autoimmune paraneoplastic diseases may be linked with TETs and can involve any organ.

Signs and symptoms of thymoma and thymic carcinoma include a cough and chest pain.

Most patients do not have signs or symptoms when first diagnosed with thymoma or thymic carcinoma. Check with your doctor if you have any of the following:

• A cough that doesn't go away.
• Shortness of breath.
• Chest pain.
• A hoarse voice.
• Swelling in the face, neck, upper body, or arms.

Tests that examine the thymus are used to help diagnose and stage thymoma and thymic carcinoma.

The following tests and procedures may be used:

• Physical exam and health 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.
• 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.
• 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).
• Biopsy: The removal of cells or tissues using a needle so they can be viewed under a microscope by a pathologist to check for signs of cancer.

Certain factors affect prognosis (chance of recovery) and treatment options.

The prognosis and treatment options depend on the following:

• Whether the cancer is thymoma or thymic carcinoma.
• Whether the cancer has spread to nearby areas or other parts of the body.
• Whether the tumor can be removed completely by surgery.
• Whether the cancer has just been diagnosed or has recurred (come back).