The mediastinum is the central compartment of the thoracic cavity. It contains the heart, the great vessels of the heart, the esophagus, the trachea, the phrenic nerve, the cardiac nerve, the thoracic duct, the thymus, and the lymph nodes of the central chest.
Mediastinal masses comprise several types and affect various organs including the thymus, trachea or esophagus (foregut cysts), pericardium (pericardial cysts) or neural structures (neurogenic tumors). Most of these masses and cysts are benign but do compress adjacent structures and can produce symptoms.
Most mediastinal masses and cysts are benign but do compress adjacent structures and produce symptoms. Due to their propensity to enlarge and get infected, surgical excision is often recommended. The Thoracic Surgery Division at UTMB has pioneered the use of Video Assisted Thoracoscopic Surgery (VATS) combined with the da Vinci® Robotic Surgical System, to achieve complete endoscopic resection of selected mediastinal cysts and tumors, with excellent outcomes.
Thymoma
Thymomas are malignant tumors that arise in the thymus gland, typically in the anterior mediastinum.
Although considered malignant, most thymomas grow slowly and tend to spread only locally, by “seeding” cells into surrounding tissues and spaces such as the pleural space (the space surrounding each lung). There is therefore often a very good chance of curing thymomas by either surgery alone or surgery followed by radiation.These localized tumors are often removed without the need for a preliminary biopsy.
More difficult thymic tumors that consist of frank carcinoma cells, and other thymic tumors that appear to invade surrounding structures on preoperative radiographic studies, are often best treated by administering preoperative chemotherapy or chemotherapy and radiation before surgical removal. These cases are discussed at our multidisciplinary care team, which consists of specialists from oncology, radiation oncology, radiology and pathology in addition to thoracic surgeons. Here, the optimal treatment plan can be designed with the combined input from all the appropriate experts. These tumors require a preoperative needle biopsy or surgical biopsy to confirm the diagnosis before giving preoperative therapies. Surgery is then generally carried out if it is felt to be possible and there has been at least some shrinkage in response to the preoperative treatment.
The most common surgical incision through which to remove a thymoma is a median sternotomy. This is a vertical incision through the breast bone that provides excellent exposure of the anterior mediastinum. Since no chest wall muscles are cut with this incision, postoperative pain is modest, and recovery is not prolonged. Smaller thymomas may be treated with video-assisted thoracoscopic surgery – see Lung Cancer section of this website.
Staging of Thymoma
Tumors caught in the early stages have relatively high cure rates; your physician will discuss your treatment options and prognosis with you.
Surgical Treatment
Surgical removal of the thymus gland (thymectomy) has had a role in the management of patients with thymoma for over 70 years. Although it has never been studied versus medical therapy in a randomized trial (where patients are “randomized” to either have surgery or have no surgery), many non-randomized studies suggest that the operation is beneficial. While very few patients have a complete remission of the disease without thymectomy, 30-40% of patients will have a complete remission after surgery.
At UTMB, we are able to perform thymectomy using Video-Assisted Thoracic Surgery (VATS) for most patients through a single, 5 cm long incision at the base of the neck. This operation, called transcervical thymectomy can be performed with very little risk or discomfort. Patients return home the day of surgery or the following day, and they generally return to their usual activities within a week. The alternative procedure – thymectomy through a median sternotomy – has a substantially increased complication rate in patients with myasthenia gravis, who are susceptible to lung and other complications due to their muscle weakness.