Ann Thorac Surg 2002;74:578-579
© 2002 The Society of Thoracic Surgeons
Case report
Thoracic intrathymic thyroid and cervical goiter: single-stage resection
Augustine T.M. Tang, FRCSEd*a,
Mark J. Johnson, BS, BMa,
Bruce Addis, FRCPatha,
David F. Weeden, FRCSa
a Department of Thoracic Surgery, Southampton General Hospital, Southampton, United Kingdom
Accepted for publication February 18, 2002.
* Address reprint requests to Mr Tang, Department of Thoracic Surgery, Wessex Regional Cardiac and Thoracic Unit, Southampton General Hospital, Tremona Rd, Southampton SO16 6YD, United Kingdom
e-mail: gus{at}tang-family.org
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Abstract
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Ectopic thyroid tissue in the chest is rare. We report a case of a euthyroid patient with benign ectopic thyroid tissue presenting as a thymic mass in association with a multinodular goiter. Both disorders were managed successfully by surgical intervention.
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Introduction
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Simultaneous disorders of the thyroid and thymus have been reported [1]. Ectopic thyroid tissue in the chest has been described in the heart and lung in ddition to two documented cases in the thymus [2–5]. We report the case of a patient with ectopic thyroid tissue presenting as a thymic mass in association with a multinodular goiter, both of which were completely resected surgically.
A 55-year-old man who drove a heavy-goods vehicle was seen with progressive visual impairment and intermittent chest pain. He was an ex-smoker of ten cigarettes per day and had an unremarkable medical history. Subsequent investigations into the acute visual disturbances revealed a pituitary macroadenoma, which was surgically removed. During the neurosurgical workup, a cervical goiter was found, and the patient was clinically euthyroid. The free serum tetraiodothyronine level was 10.9 pmol/L (laboratory reference range, 8–22 pmol/L), and the thyroid-stimulating hormone level was 0.16 mU/L (laboratory reference range, 0.3 – 3.5 mU/L). A routine preoperative plain chest radiograph revealed an upper mediastinal mass. This was confirmed on axial computed tomographic scanning as a large cervical goiter with mild compression of the upper trachea (Fig 1).
Thoracic imaging also demonstrated a separate solid contrast-enhanced mass in the left anterior mediastinum contiguous to the thymus gland, which possibly accounted for the chest symptoms (Fig 2).
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Fig 1. Axial computed tomographic scan of the thoracic inlet demonstrating a large goiter (G) with mild compression and deviation of the upper trachea.
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Fig 2. Axial computed tomographic scan of the thorax with contrast enhancement revealing a large anterior mediastinal mass (M) to the left of the main pulmonary artery. The mass appeared to be contiguous to the thymus and was enhanced with contrast medium.
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As both the clinical and radiological clues suggested that the mediastinal mass was likely to represent either a dermoid tumor or a thymoma either of which would require surgical resection, a combined subtotal thyroidectomy and thymectomy was recommended after full thoracic and endocrine evaluation. Further biopsy for histological diagnosis was avoided at this stage to prevent capsular penetration and potential tumor seeding of the mediastinum should the mass be a malignant thymoma. Almost all of the left lobe and 90% of the right lobe of the thyroid were removed through a standard cervical approach. The right parathyroid glands were preserved. Through a median sternotomy, a large mass measuring 90 x 75 x 65 mm was found in the left inferior pole of the thymus, which had no direct physical continuity with the cervical goiter. Inflammatory adhesions were divided, and the left pleura was opened deliberately. This mass was carefully separated from the phrenic nerve, which was preserved. The left internal thoracic artery and thymic veins were ligated and divided in the process. There was no apparent macroscopic capsular invasion by the tumor, which was removed en bloc. The chest was closed in a standard fashion.
The patient made an uneventful postoperative recovery and was discharged home on the sixth postoperative day. At the 3-month follow-up, the patient was euthyroid on a regime of oral thyroxine (100 µg daily) with complete resolution of the preoperative symptoms including chest pain. The wound had healed well with little residual discomfort.
Histopathological examination of the resected specimens confirmed a multinodular goiter with no evidence of malignancy. The thymus gland contained a large, well-encapsulated irregular mass with multiple small cysts consisting of multinodular thyroid tissue in an otherwise normal thymus (Fig 3).
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Fig 3. Histological specimen demonstrating thyroid nodule (T) with a thickened capsule (C). Thymic tissue as indicated by the Hassall’s corpuscle (arrow) is dispersed in the surrounding mediastinal fat. (Hematoxylin and eosin; x40 before percent reduction.)
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Comment
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Concomitant pathological processes, both malignant and benign, affecting the thyroid and thymus glands have been reported, but they are unusual. Beddingfield and co-workers [1] presented the case of a patient with simultaneous carcinomas of the thymus and thyroid glands; thymic hyperplasia in the presence of hyperthyroidism was described in another patient [1].
Ectopic thyroid tissue tends to be found along the embryological line of descent of the gland but has been described in more unusual locations including the lateral aspect of the neck in a subplatysmal plane [6]. However, ectopic thyroid tissue in the thorax is a true rarity. Isolated examples have been found in both the lung and the heart. In the latter instance, the ectopic thyroid tissue tends to occur preponderantly in the right ventricle [2, 4, 5], although an exceptional case was reported in the left ventricular outflow tract [3].
Thoracic intrathymic thyroid was introduced as a clinical entity by Spinner and coauthors [5] in 1994. In 2 patients, thyroid tissue presenting as a mediastinal mass in close association with the thymus gland was reported in the absence of any clinical, biochemical, or radiological evidence of abnormality in the thyroid itself [5]. These patients were also noted to be both clinically and biochemically euthyroid. The authors suggested that the embryonic development of the thyroid gland underpins their observations of such clinical anomalies. The thyroid originates from a diverticulum at the base of the pharyngeal part of the tongue. It is subsequently drawn into the neck anterior to the trachea as the heart descends during fetal growth. The relationship between the thyroid and the heart accounts for the spectrum of anomalies ranging from lingual thyroid, where there is reduced contact with the heart, to intracardiac thyroid, where contact is intimate. Accordingly, the close proximity of the thyroid diverticulum to the third pair of branchial pouches, from which the thymus develops, could explain the occurrence of intrathymic thyroid tissue.
Our case is remarkable in two respects: it demonstrates the rare occurrence of simultaneous disorders in the thyroid and thymus glands, and it supports thoracic intrathymic thyroid as a clinical entity in a patient with no histological evidence of thyroid malignancy. Such a unique problem can be dealt with in a single surgical setting with an excellent outcome.
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References
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- Beddingfield G.W., Campbell D.C., Jr, Hood R.H., Jr, Dooley B.N. Simultaneous disorders of thyroid and thymus: report of Two Cases. Ann Thorac Surg 1967;4:445-450.[Free Full Text]
- Richmond I., Whittaker J.S., Deiraniya A.K., Hassan R. Intracardiac ectopic thyroid: a case report and review of published cases. Thorax 1990;45:293-294.[Abstract/Free Full Text]
- Baykut D., Fiegen U., Krian A., Thiel A. Ectopic thyroid tissue in the left ventricular outflow tract. Ann Thorac Surg 2000;69:620-621.[Abstract/Free Full Text]
- Bando T., Keiichiro G., Ishikawa K., Kuniyoshi M., Kuda T. Ectopic intrapulmonary thyroid. Chest 1993;103:1278-1279.[Abstract/Free Full Text]
- Spinner R.J., Moore K.L., Gottfried M.R., Lowe J.E., Sabiston D.C., Jr Thoracic intrathymic thyroid. Ann Surg 1994;220:91-96.[Medline]
- Pang Y.T. Ectopic multinodular goitre. Singaporé Med J 1998;39:169-170.[Medline]
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Abstract
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