Ann Thorac Surg 2009;88:656-659. doi:10.1016/j.athoracsur.2009.02.002
© 2009 The Society of Thoracic Surgeons
Case Reports
Posterior Mediastinal Ectopic Thyroid: An Unusual Cause for Dysphagia
Recep Demirhan, MDa,
Burak Onan, MDa,*,
Kursad Oz, MDa,
Sevinc Hallac Keser, MDb,
Aylin Ege Gul, MDb,
Ismihan Selen Onan, MDc
a Department of Thoracic Surgery, Dr Lutfi Kirdar Kartal Education and Research Hospital, Istanbul, Turkey
b Department of Pathology, Dr Lutfi Kirdar Kartal Education and Research Hospital, Istanbul, Turkey
c Department of Cardiovascular Surgery, Istanbul Bilim University, Istanbul, Turkey
Accepted for publication February 2, 2009.
* Address correspondence to Dr Onan, Dr Lutfi Kirdar Kartal Egitim ve Arastirma Hastanesi, Gogus Cerrahi Klinigi, Semsi Denizer Caddesi, E–5 Karayolu Cevizli Mevkii Kartal, Istanbul, 34890, Turkey (Email: burakonan{at}hotmail.com).
 |
Abstract
|
|---|
Posterior mediastinum is an atypical localization for the occurrence of ectopic thyroid. We present a case of a 62-year-old man who was admitted to the emergency department with atypical chest pain and dysphagia. The patient was diagnosed as having a true posterior mediastinal ectopic thyroid, which caused esophageal compression. The tumor was completely resected through a sternotomy, with favorable outcome and relief of symptoms.
|
Introduction
|
|---|
Ectopic thyroid may develop anywhere from the foramen cecum to the lower neck due to abnormal migration of the thyroid tissue. True primary ectopic thyroid tumors are encountered in less than 1% of all goiters [1], but the incidence of posterior mediastinal localization is not clear. Although different types of pathologies, including neurogenic, lymphatic, mesenchymal, pleural, osteal, and esophageal tumors can be diagnosed in the posterior mediastinum, ectopic thyroid is still considered a diagnostic possibility. The tumor, if of considerable size, may cause obstructive symptoms related to tracheal, esophageal, or venous compression. We present a patient with ectopic thyroid in the posterior mediastinum that caused esophageal compression and dysphagia.
A 62-year-old man was admitted to the emergency department with atypical chest pain, and stated that he was unable to swallow solid foods for the last 3 months. A routine chest roentgenogram established a diagnosis of mediastinal enlargement to the right hemithorax. A subsequent chest computed tomography scan confirmed a large posterior mediastinal mass compressing the esophagus and protruding into the right hemithorax (Fig 1). The mass extended from the level of innominate vein superiorly, posterior to the trachea, the right bronchi, superior vena cava, and the right main pulmonary artery, with severe esophageal compression to the right hemithorax. The scan showed no tumor growth in the thoracic inlet, anterior mediastinum, and cervical regions. Therefore, the mass was thought to be an isolated posterior mediastinal lesion, and an extension of any pathology within the thoracic cavity or from the cervical region was excluded.
View larger version (112K):
[in this window]
[in a new window]
|
Fig 1. Preoperative computed tomography image shows posterior mediastinal ectopic thyroid of 70 x 55 mm in transverse diameter causing esophageal compression. The lesion protruding into the right hemithorax is localized posterior to the trachea and superior vena cava and inferior to the innominate vein.
|
|
The patient was clinically euthyroid and well, without having a weight loss within last few months. Cardiovascular and respiratory examinations did not reveal an abnormality suggesting venous obstruction or tracheal stenosis. There was no abnormality to explain the cause for dysphagia, including neurologic disorders. Preoperative blood chemistry analysis showed the thyroid-stimulating hormone (TSH) level was mildly elevated, while free T3 and T4 level was normal.
We often find needle biopsy useful in the preoperative evaluation of mediastinal masses, and we did wish to obtain one in this case; however, this was not possible because the invasive radiologist was unavailable in our clinic at that time. Esophagoscopy did not reveal any sign of transmural esophageal invasion but suggested an external compression by the tumor. We believed this mass could be a benign pathology such as neurogenic or germ cell tumor because it was a solitary lesion with a regular border and did not show an aggressive growth pattern. Thus, an operation was performed to remove the mass and to relieve esophageal compression.
Thoracotomy is a possible and frequently used approach in this type of tumor located in posterior mediastinum. However, we preferred sternotomy to provide a better exposure and to gain an optimum control of the vascular structures. After dissecting through the retrosternal fat pads, the mediastinal great vessels, including superior vena cava, innominate vein, and the right pulmonary artery were exposed and secured with silicon elastomer loops. The pleura on the right were entered to dissect the posterior side of the mass.
The tumor was identified as lying posterior to the right pulmonary artery and the junction between superior vena cava and the right atrium. It was gently extracted by careful blunt dissection from the posterior mediastinum and measured 70 x 55 x 50 mm (Fig 2). The blood supply of the tumor originated from the innominate artery and the left innominate vein, and all were subsequently suture ligated. The right phrenic nerve and great vascular structures were protected during the procedure. At the end of the procedure, we believed that resection of this mass could also have been performed with a thoracotomy.
This ectopic thyroid was completely encapsulated and totally localized in the posterior mediastinum as an isolated intrathoracic tumor causing dysphagia. Pathologic sections confirmed the lesion as ectopic thyroid (Fig 3). The patient was discharged home uneventfully on postoperative day 6. He is currently well 9 months after the procedure.
View larger version (143K):
[in this window]
[in a new window]
|
Fig 3. Photomicrograph of the tumor shows the thyroid cells in high magnification (original magnification x200).
|
|
|
Comment
|
|---|
The posterior mediastinum is an atypical localization for the occurrence of thyroid tumors, including primary ectopic goiters and mediastinal recurrences after thyroid operations. Most of these tumors are known to develop in the anterosuperior mediastinum, the so-called cervicomediastinal region [2]. The incidence of mediastinal goiter varies from 0.16% to 3.3% in thyroid tumors and 4.4% in mediastinal tumors [2–4]. According to autopsy studies, ectopic goiters have a prevalence of between 7% and 10%, but true primary ectopic thyroid tumors are encountered in less than 1% of all goiters [1, 5]. The true incidence of ectopic thyroid in the posterior mediastinum is not clear, however.
Within the first trimester of gestation, the thyroid gland migrates caudally to its normal pretracheal position. Abnormal migration causes aberrant localization of the thyroid tissue anywhere from the foramen cecum, which is located at the junction of the anterior two-thirds and posterior one-third of the tongue, to the lower neck. Of the reported cases of ectopic thyroid, 90% are found in the base of the tongue and termed "lingual thyroid" [6], whereas only 10% lie in the cervical region and rarely below the plane of the thoracic inlet, involving mostly anterior mediastinum. Therefore, it is an unusual event to discover ectopic thyroid in the posterior mediastinum.
Primary ectopic goiters are isolated intrathoracic lesions with a blood supply that typically comes from intrathoracic vessels. The other criteria on diagnosis include a normal cervical gland without a history of surgery or malignancy [1]. In the differential diagnosis of mediastinal thyroid pathologies, substernal goiters and recurrences after thyroid surgery are included. Substernal goiters are generally extensions of an enlarged cervical goiter into the anterosuperior mediastinum. On the other hand, fewer than 20% of the patients after thyroid operations have a significant intrathoracic component, which generally develops in the anterior and middle mediastinum with blood supply from the cervical region rather than posterior compartment [4].
Esophageal compression as a mechanical cause of dysphagia has been previously reported. However, this mass effect was noted in the cervical region due to enlarged gland of multinodular goiter or ectopic lingual thyroid [7, 8]. In our literature review, we could not find a report on ectopic thyroid that developed in the posterior mediastinum causing severe esophageal compression, and believed that this was a rare event to report as a cause for dysphagia.
The patient in the current case was previously asymptomatic, but complained of atypical chest pain and progressive dysphagia. He was diagnosed with chest computed tomography imaging as having a posterior mediastinal tumor causing esophageal compression. Due to the localization and close relation of the mass with vascular structures, an operation was performed through a sternotomy. Perioperative findings and pathologic evaluation of the tumor help to diagnose ectopic thyroid.
The mechanism for the growth of such a tumor is not clear. According to certain theories, mediastinal goiters may arise from distant ectopic tissues due to increased TSH production after cervical thyroidectomy [2]. This knowledge associated with metabolic as well as embryologic processes could be the only explanation. Nevertheless, slightly increased TSH level, benign nature of the tumor, the absence of previous thyroid surgery, radiologic findings, and perioperative diagnosis of blood supply originating from thoracic vessels confirmed the diagnosis of ectopic thyroid in this patient.
Ectopic thyroid is an unusual presentation of thyroid disease and all mediastinal tumors. Most of these patients are clinically euthyroid, but hyperthyroidism can be observed. Serum thyroid tests may help the preoperative diagnosis and postoperative follow-up. Thyroid nuclear scans may be useful in diagnosis and in clinical management. A positive uptake confirms a thoracic goiter, but a negative scan does not exclude the diagnosis. In patients with previous thyroid operation, nuclear scans may help to evaluate the mediastinum for suspected recurrences. Chest computed tomography is a valuable imaging modality. Clinical presentation changes according to the localization and size of the tumor. Although most patients are asymptomatic, if the mass is of considerable size, dry cough, wheezing, dysphagia, or signs of venous obstruction can be seen.
Surgical resection for ectopic thyroid localized in the posterior mediastinum is recommended when obstructive symptoms occur in relation to its mass effect, such as tracheal, esophageal, or superior vena cava compression [3]. Thoracotomy and partial or full median sternotomy are the possible approaches for surgical resection because they offer greater exposure and access for complete excision and control of intraoperative bleeding.
In conclusion, we present a true posterior mediastinal ectopic thyroid resected through a median sternotomy with complete excision and relief of dysphagia.
|
References
|
|---|
- Gamblin TC, Jennings GR, Christie 3rd DB, Thompson Jr WM, Dalton ML. Ectopic thyroid Ann Thorac Surg 2003;75:1952-1953.[Abstract/Free Full Text]
- Vadasz P, Kotsis L. Surgical aspects of 175 mediastinal goiters Eur J Cardiothorac Surg 1998;14:393-397.[Abstract/Free Full Text]
- Newman E, Shaha AR. Substernal goiter J Surg Oncol 1995;60:207-212.[Medline]
- Tsang F, Wan I, Lee TW, Ng SK, Yim A. Management of retrosternal goiter with superior vena cava obstruction Heart Lung Circ 2007;16:312-314.[Medline]
- Sand J, Pehkonen E, Mattila J, Seppanen S, Salmi J. Pulsating mass at the sternum. A primary carcinoma of ectopic mediastinal thyroid. J Thorac Cardiovasc Surg 1996;112:833-835.[Free Full Text]
- Neinas FW, Gorman CA, Devine KD, Woolner LB. Lingual thyroid. Clinical characteristics of 15 cases. Ann Intern Med 1973;79:205-210.[Abstract/Free Full Text]
- Gallo A, Leonetti F, Torri E, Manciocco V, Simonelli M, De Vincentiis M. Ectopic lingual thyroid as unusual cause of severe dysphagia Dysphagia 2001;16:220-223.[Medline]
- Alfonso A, Christoudias G, Amaruddin Q, Herbsman H, Gardner B. Tracheal or esophageal compression due to benign thyroid disease Am J Surg 1981;142:350-354.[Medline]
Top
Abstract
Introduction
