The mediastinum is the space situated in the middle of the chest cavity, between the lungs. It contains many structures including the thymus gland, heart & great vessels, nerves, lymph nodes and the esophagus. Diseases of the mediastinum that are not heart related include tumors and infections which are often times life-threatening and demand prompt diagnosis. Following is a brief summary of these potential disease processes that are within the scope of practice of a thoracic surgeon.
The thymus gland is located in most anterior part of the mediastinum and is responsible for producing immune system cells from embryonic development through childhood. As a person ages, the thymus gland gradually involutes and is replaced with fatty tissue. Two generic processes can affect the thymus, both related to enlargement of the gland: thymic hyperplasia and thymic tumors, most commonly a thymoma.
While many patients experience no symptoms, others experience the following:
- swelling of the face
- chest pain
- muscle weakness (especially in the eyes, neck, and chest)
- shortness of breath
Enlargement of the thymus gland is usually seen by chest x-ray or CT scan, and its presence usually requires surgical intervention, either as part of the treatment plan or to obtain a more precise diagnosis. Therefore, a thoracic surgeon should always be involved in the evaluation of these patients.
Removal of the thymus gland can be performed using different techniques. Traditionally, a sternotomy (splitting of the breast bone) is needed because such an incision allows the best exposure of the mediastinum. Alternatives are through the use of video-assisted thoracic surgery (video camera with small incisions) or by robotic surgery. Only a thoracic surgeon can determine which technique is best for each individual patient. To read more about thymomas, click here.
Myasthenia gravis is an autoimmune disease which manifests as a neuromuscular system disorder with muscle weakness and easy fatigability. There is a strong association between myasthenia and thymomas, although its causal and effect relationship is not well understood.
The treatment of myasthenia gravis involves oral medication. When a thymoma is also present, surgical removal is mandatory. The indication for surgical removal of the thymus gland in the setting of myasthenia gravis, but in the absence of a thymoma, is controversial. Many specialists do favor its removal and there is an ongoing international multi-institutional trial that will try to settle this discussion. At minimum, all patients with myasthenia gravis should discuss the pros and cons of surgical resection of the thymus gland with their physicians. To learn more about myasthenia gravis, click here.
Lymphoma is a term for cancers that occur in cells of the lymphatic (immune) system. These cancers are subdivided into 2 big groups of either Hodgkin’s Lymphoma or non-Hodgkin’s Lymphoma. A multitude of specific subtypes exists, depending on which cell type is involved. Because lymph cells travel in the blood stream throughout the body, these cancers represent a systemic disease for which chemotherapy is the mainstay of treatment.
Lymphoma is diagnosed by removing tissue samples of enlarged lymph nodes. The location of these nodes will vary from each individual patient. Frequently enlarged lymph nodes will present as an anterior mediastinal mass in which case a thoracic surgeon will be involved in providing adequate tissue biopsies. These biopsies can be obtained by endoscopic or surgical techniques. Endoscopy involves the use of a camera at the tip of a scope that is introduced in the esophagus or the wind pipe (trachea and bronchi). These nodes can be sampled with or without the assistance of endoscopic (EUS) ultrasound or endobronchial ultrasound (EBUS). Sometimes these techniques are not sufficient for diagnosis and a surgical procedure is needed, either through a mediastinoscopy (a small incision above the breast bone) or by video-assisted surgery (VATS).
Germ Cell Tumors
Germ cell tumors are common tumors of the reproductive system (testis and ovaries) but occasionally occur in the mediastinum, either as a tumor spread (metastasis) or as a primary tumor. They can be broadly classified into seminomas and non-seminomas tumors and treatment requires a multidisciplinary approach in which a team of phycisians, including thoracic surgeons, medical oncologists and radiation oncologists discuss the best strategy for each patient. More often than not, surgical removal is indicated, either before or after chemo and radiation therapy and the available options are the same as described for thymus gland tumors.