The mediastinum is the area in the middle part of the chest. It is the space behind the sternum (breast bone) and in front of the spine (back bone) between the lungs. It extends from the neck to the diaphragm. The mediastinum is usually separated into three areas: anterior, middle, and posterior.
In general, mediastinal tumors are rare. They are found most frequently in people between the ages of 30 and 50, but they can occur at any age. Adults are more likely to have anterior mediastinal tumors. Children are more likely to have posterior mediastinal tumors. Anterior mediastinal tumors are more likely to be malignant (cancerous), and posterior mediastinal tumors are more likely to be benign (non-cancerous).
The most common type of anterior mediastinal mass is a thymoma. There are different types of thymoma, but the majority are well circumscribed, benign, and surrounded by a fibrous capsule. About 1/3 are more aggressive and grow through the capsule invading surrounding tissues and fat. People can also develop thymic carcinomas (cancers). Other causes of anterior mediastinal masses include Lymphoma, Germ Cell tumors, and substernal thyroid glands.
Pericardial and bronchial cysts are the most common abnormalities found in the middle mediastinum, and are often benign.
Posterior mediastinal tumors most commonly arise from the nerves, and these tumors are most commonly benign.
Many mediastinal tumors do not cause any specific symptoms, and can be found incidentally on chest imaging (CT scan or CXR). If the masses cause symptoms, these symptoms are often related to pressure from the growing mass on surrounding structures or the underlying disease and can include: cough, shortness of breath, chest pain, flushing, fevers, chills, night sweats, hoarseness, unexplained weight loss. Once identified or suspected, mediastinal masses are usually imaged with CT scan. Blood tests can be useful in determining certain types of mediastinal tumors. Some tumors require a biopsy for diagnosis, which can be done in a variety of ways. Treatment is dependent on the type of mediastinal tumor, its location, and symptoms. For example, lymphomas may need a minimally invasive surgery for biopsy, but are generally treated with chemotherapy, followed by possible radiation. Germ cell tumors are also often treated with the non-surgical approach. Thymomas and posterior mediastinal nerve sheath tumors on the other hand are treated surgically, and can often be removed using minimally invasive, including robotic assisted, thoracic surgery. Some masses can be observed with serial imaging if they are not cancerous and are not causing any symptoms.