The thymus is a small organ that is part of the lymphatic system and is located in the chest, behind the breastbone. The thymus produces white blood cells, called lymphocytes, that 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 divided into subtypes, depending on the types of cells in which the cancer began. Also called type C thymoma.
Signs and symptoms
Thymoma and thymic carcinoma may not cause early signs or symptoms. The cancer may be diagnosed during a routine chest x-ray. Signs and symptoms of thymic malignancies include a cough that doesn’t go away and chest pain, breathlessness or other conditions.
The following tests and medical procedures may be used to examine the thymus and detect thymoma or thymic carcinoma :
- 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.
- A biopsy of the tumor is done to diagnose the disease. The biopsy may be done before or during surgery (a mediastinoscopy or mediastinotomy), using a thin needle to remove a sample of cells. This is called a fine-needle aspiration (FNA) biopsy. Sometimes a wide needle is used to remove a sample of cells and this is called a core biopsy. A pathologist will view the sample under a microscope to check for cancer. If thymoma or thymic carcinoma is diagnosed, the pathologist will determine the type of cancer cell in the tumor. There may be more than one type of cancer cell in a thymoma. The surgeon will decide if all or part of the tumor can be removed by surgery. In some cases, lymph nodes and other tissues may be removed as well.
Staging thymic malignancies:
Thymoma and thymic carcinoma are usually diagnosed, staged, and treated during surgery.
The following stages are used for thymoma:
At this stage, the cancer is found only within the thymus. All cancer cells are inside the capsule (sac) that surrounds the thymus.
In stage II, the cancer has spread through the capsule and into the fat around the thymus or into the lining of the chest cavity.
In stage III, the cancer has spread to nearby organs in the chest, including the lung, the sac around the heart, or large blood vessels that carry blood to the heart.
In stage IV, the cancer has spread to distant organs.
When diagnosed, thymic carcinomas have usually already spread to other parts of the body.
Different types of treatments are available for patients with thymoma and thymic carcinoma. Some treatments are standard (currently used treatments), and some are being tested in clinical trials. A treatment clinical trial is a research study meant to help improve current treatments or obtain information on new treatments for patients with cancer. When clinical trials show that a new treatment is better than the standard treatment, the new treatment may become the standard treatment.