Advertisement

Transsternal Thymectomy

  • Anna Maria Ciccone
    Affiliations
    From the Division of Cardiothoracic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO
    Search for articles by this author
  • Bryan F. Meyers
    Correspondence
    Address reprint requests to Bryan F. Meyers, MD, 3108 Queeny Tower, One Barnes-Jewish Hospital Plaza, St. Louis, MO 63110
    Affiliations
    From the Division of Cardiothoracic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO
    Search for articles by this author
      Thymoma is unusual but nonetheless the most common tumor of the anterior mediastinum. This tumor is unique in its indolent growth and its frequent association with paraneoplastic syndromes, hematologic syndromes, and autoimmune disorders. By far the most common of these paraneoplastic syndromes is myasthenia gravis, present in 30% to 40% of patients with thymoma.
      The diagnosis of thymoma is usually made clinically. Approximately one third of patients with thymoma present without symptoms, typically with a mass detected on chest x-ray obtained for other reasons. Another one third of patients present with vague nonspecific symptoms, such as pressure in the chest or nonspecific pains, or with local symptoms, such as dyspnea, dysphagia, cough, hoarseness, and respiratory infection. Less commonly, patients exhibit superior vena cava syndrome, tracheal stenosis, or bronchial stenosis. The remainder of patients present with signs and symptoms of myasthenia gravis or other paraneoplastic disorders.
      Despite contradictory viewpoints regarding histology, pathology, staging, and nonsurgical management, the most important therapeutic modality for thymoma is surgical resection.

      Surgical Technique

      Figure thumbnail fx1
      1(A, B) After induction of general anesthesia, the patient is placed in a supine position with the arms at the sides. A pad can be placed behind the patient's shoulders to extend the neck and improve access to the upper end of the incision. The incision is made from beneath the suprasternal notch to the lowermost point of the xiphisternum and extended to the periosteum of the sternum and linea alba with electrocautery. The sternum is divided at the midline along its length with a sternal saw with a vertical oscillating blade.
      Figure thumbnail fx2
      2A sternal spreader with broad blades is positioned and opened gradually to avoid fracture of the sternum and upper ribs and neurologic insult. Fatty tissue behind the sternum is cleared laterally with a swab, and the pretracheal fascia is exposed as it extends down from the neck to form the anterior capsule of the thymus.
      Figure thumbnail fx3
      3After the thin fascia around the perimeter of the thymus is incised, blunt and sharp dissection are used to free the gland from the pericardium and the adjacent mediastinal pleura, exposing and reflecting cephalad the lower poles. At this time, the pleural spaces are usually opened to allow early visualization of the phrenic nerves. If the thymoma abuts the mediastinal pleura, then this pleura should be left attached to the mass and resected with it. Mobilization is continued from caudal to cranial, using the electrocautery with caution to avoid unintentional injury of the small arterial branches from the internal mammary artery. These branches should be identified and divided between ligatures on each side. Additional blood supply is encountered arising from the inferior thyroid artery at the upper extent of the dissection.
      Figure thumbnail fx4
      4As the dissection plane approaches the innominate vein, one to three thymic veins are encountered. These veins enter the innominate vein inferiorly and anteriorly and should be ligated and transected. With the thymus reflected upward, the entire anterior surface of the pericardium is exposed. When the tumor abuts the pericardium, the surgeon should not hesitate to resect with liberal margins any portion of the pericardium attached to the tumor.
      Figure thumbnail fx5
      5Retraction of the upper end of the wound allows identification of the two upper poles of the thymus passing upward into the neck. Gentle traction of the body of the thymus and blunt dissection of the cervical extension of each lobe will deliver these into the wound. After the thyrothymic ligament and the adjacent veins are divided, the upper poles of the thymus are freed.
      Figure thumbnail fx6
      6It is important to remove all of the adipose tissue to ensure complete removal of any collections of identifiable macroscopic and microscopic thymic tissue that may be found as additional mediastinal lobes and islets of tissue outside the thymic capsule extending from the neck to the diaphragm.
      Figure thumbnail fx7
      7To achieve an “extended” thymectomy, careful exploration of both pleural spaces is necessary, searching for supernumerary lobes and discontinuous nodules and excision of the anterior mediastinal fat from the pericardiophrenic angles inferiorly to the neck superiorly and laterally from phrenic nerve to phrenic nerve. (Reprinted with permission.
      • Jaretzki III, A
      Thymectomy for myasthenia gravis: Analysis of the controversies regarding technique and results.
      )
      Figure thumbnail fx8
      8If an invasive tumor is found, then en bloc removal of affected structures is performed along with the total thymectomy. These resectable structures include pericardium, pleura, lung, phrenic nerve, innominate vein, vena cava, and the chest wall. Small pericardial defects do not necessitate specific reconstruction, though larger and lateral defects create a risk for cardiac herniation and should be repaired. To achieve a complete resection, all resectable mediastinal structures invaded by the mass should be resected. (A) The reconstruction after resection of pericardium and innominate vein. The reconstruction of the pericardium was achieved with Marlex mesh and and the vein was replaced with bovine pericardium. (B) The result after resection of a stage III thymoma invading innominate vein and superior vena cava and reconstruction with a ribbed polytetraflouroethylene prosthetic graft. If a single phrenic nerve is involved, then resection of the tumor and the attached nerve should be carried out according to the preoperative evaluation of the patient's respiratory status and the functional state of both nerves before surgery. If both phrenic nerves are involved and functioning preoperatively, neither should be resected and the area should be debulked only. Clips should mark those areas of residual disease to facilitate postoperative radiotherapy.
      Figure thumbnail fx9
      9After a simple thymectomy that did not include pleural entry, a suction drainage or chest tube is placed in the anterior mediastinum and brought out through a stab wound near the lower end of the incision. In the more typical case of bilateral opened pleural spaces, however, one or two pleural tubes are required. Once the resection and reconstruction have been completed, the sternum is approximated with four to eight stainless steel wires passed around the sternum through the intercostal spaces.

      Results

      Operative mortality of this procedure has been nearly eliminated, and perioperative survival is excellent, with more than 95% of patients discharged from the hospital. Aggressive preoperative and postoperative management of any associated myasthenia gravis has essentially eliminated the problem of postoperative respiratory failure.
      The literature clearly indicates that surgery (particularly complete resection) is an important aspect of a multimodality approach to therapy.
      • Blumberg D
      • Port JL
      • Weksler B
      • et al.
      Thymoma: A multivariate analysis of factors predicting survival.
      • Gawrychowski J
      • Rokicki M
      • Gabriel A
      • et al.
      Thymoma--The usefulness of some prognostic factors for diagnosis and surgical treatment.
      • Sugiura H
      • Morikawa T
      • Ito K
      • et al.
      Long-term results of surgical treatment for invasive thymoma.
      • Regnard JF
      • Magdeleinat P
      • Dromer C
      • et al.
      Prognostic factors and long-term results after thymoma resection: A series of 307 patients.
      • Wilkins KB
      • Sheikh E
      • Green R
      • et al.
      Clinical and pathologic predictors of survival in patients with thymoma.
      • Schneider PM
      • Fellbaum C
      • Fink U
      • et al.
      Prognostic importance of histomorphologic subclassification for epithelial thymic tumors.
      • Masaoka A
      • Monden Y
      • Nakahara K
      • et al.
      Follow-up study of thymoma with special reference to their clinical stages.
      • Thomas Jr, CR
      • Wright CD
      • Loehrer Sr, PJ
      Thymoma: State of the art.
      • Shin DM
      • Komaki R
      • Nesbitt J
      • et al.
      A multidisciplinary approach to therapy for unresectable malignant thymoma.
      • Venuta F
      • Rendina EA
      • Pescarmona EO
      • et al.
      Multimodality treatment of thymoma: A prospective study.
      • Wilkins Jr, EW
      • Grillo HC
      • Scannell JG
      • et al.
      Role of staging in prognosis and management of thymoma.
      • Urgesi A
      • Monetti U
      • Rossi G
      • et al.
      Role of radiation therapy in locally advanced thymoma.
      • Park HS
      • Shin DM
      • Lee JS
      • et al.
      Thymoma. A retrospective study of 87 cases.
      • Loehrer Sr, PJ
      • Chen M
      • Kim K
      • et al.
      Cisplatin, doxorubicin and cyclophosphamide plus thoracic radiation therapy for limited-stage unresectable thymoma: An intergroup trial.
      The actual strategies used in our institutions for locally advanced thymomas are multidisciplinary with complete surgical resection when feasible. Neoadjuvant chemotherapy has replaced preoperative radiation therapy in the management of presumed invasive thymomas.
      The 10-year actuarial overall survival is 60% to 70%. The overall likelihood of recurrence of a completely resected thymoma ranges from 10% to 30%.
      • Regnart JF
      • Zinzindohoue F
      • Magdeleinat P
      • et al.
      Results of re-resection for recurrent thymomas.
      Most authors agree that prolonged follow-up is needed for patients who undergo thymoma resection, because recurrence may occur several years after the operation. Some authors have pointed out that tumor recurrence can happen in most stages and in most histologic types, but most commonly in stage III or IV epithelial thymomas. Recurrences often appear as a local or regional rather than a hematogenous spread. Considering the encouraging results of the aggressive surgical approach, some authors recommend re-resection in resectable recurrent thymomas.
      • Regnart JF
      • Zinzindohoue F
      • Magdeleinat P
      • et al.
      Results of re-resection for recurrent thymomas.
      • Kirschner PA
      Reoperation for thymoma: Report of 23 cases.
      New chemotherapy regimens are leading to multimodality therapies, and data suggest that the response rate to multidrug, cisplatin-based therapy ranges from 50% to 90%. Nonetheless, it will remain difficult to determine their benefits, considering this tumor's rarity, heterogeneity, and indolent natural history.

      References

        • Blumberg D
        • Port JL
        • Weksler B
        • et al.
        Thymoma: A multivariate analysis of factors predicting survival.
        Ann Thorac Surg. 1995; 60: 908-914
        • Gawrychowski J
        • Rokicki M
        • Gabriel A
        • et al.
        Thymoma--The usefulness of some prognostic factors for diagnosis and surgical treatment.
        Eur J Surg Oncol. 2000; 26: 203-208
        • Sugiura H
        • Morikawa T
        • Ito K
        • et al.
        Long-term results of surgical treatment for invasive thymoma.
        Anticancer Res. 1999; 19: 1433-1438
        • Regnard JF
        • Magdeleinat P
        • Dromer C
        • et al.
        Prognostic factors and long-term results after thymoma resection: A series of 307 patients.
        J Thorac Cardiovasc Surg. 1996; 112: 376-384
        • Wilkins KB
        • Sheikh E
        • Green R
        • et al.
        Clinical and pathologic predictors of survival in patients with thymoma.
        Ann Surg. 1999; 230: 562-574
        • Schneider PM
        • Fellbaum C
        • Fink U
        • et al.
        Prognostic importance of histomorphologic subclassification for epithelial thymic tumors.
        Ann Surg Oncol. 1997; 4: 46-56
        • Masaoka A
        • Monden Y
        • Nakahara K
        • et al.
        Follow-up study of thymoma with special reference to their clinical stages.
        Cancer. 1981; 48: 2485-2492
        • Thomas Jr, CR
        • Wright CD
        • Loehrer Sr, PJ
        Thymoma: State of the art.
        J Clin Oncol. 1999; 17: 2280-2289
        • Shin DM
        • Komaki R
        • Nesbitt J
        • et al.
        A multidisciplinary approach to therapy for unresectable malignant thymoma.
        Ann Intern Med. 1998; 129: 100-104
        • Venuta F
        • Rendina EA
        • Pescarmona EO
        • et al.
        Multimodality treatment of thymoma: A prospective study.
        Ann Thorac Surg. 1997; 61: 1585-1592
        • Wilkins Jr, EW
        • Grillo HC
        • Scannell JG
        • et al.
        Role of staging in prognosis and management of thymoma.
        Ann Thorac Surg. 1991; 51: 888-892
        • Urgesi A
        • Monetti U
        • Rossi G
        • et al.
        Role of radiation therapy in locally advanced thymoma.
        Radiother Oncol. 1990; 19: 273-280
        • Park HS
        • Shin DM
        • Lee JS
        • et al.
        Thymoma. A retrospective study of 87 cases.
        Cancer. 1994; 73: 2491-2498
        • Loehrer Sr, PJ
        • Chen M
        • Kim K
        • et al.
        Cisplatin, doxorubicin and cyclophosphamide plus thoracic radiation therapy for limited-stage unresectable thymoma: An intergroup trial.
        J Clin Oncol. 1997; 15: 3093-3099
        • Regnart JF
        • Zinzindohoue F
        • Magdeleinat P
        • et al.
        Results of re-resection for recurrent thymomas.
        Ann Thorac Surg. 1997; 61: 1593-1598
        • Kirschner PA
        Reoperation for thymoma: Report of 23 cases.
        Ann Thorac Surg. 1990; 49: 550-555
        • Jaretzki III, A
        Thymectomy for myasthenia gravis: Analysis of the controversies regarding technique and results.
        Neurology. 1997; 48: S52-S63