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J Thorac Cardiovasc Surg 1996;112:833-835
© 1996 Mosby, Inc.

BRIEF COMMUNICATIONS

PULSATING MASS AT THE STERNUM: A PRIMARY CARCINOMA OF ECTOPIC MEDIASTINAL THYROID

Tampere, Finland

Received for publication Dec. 8, 1995 Accepted for publication Dec. 21, 1995. Address for reprints: Juhani Sand, MD, Department of Surgery, Tampere University Hospital, FIN-33521 Tampere, Finland.

During embryogenesis the descent of the thymus, thyroid, and parathyroid glands may be disturbed, leading to various possibilities for anomalous locations of each gland. One of the aberrant locations of the ectopic thyroid is the mediastinum. Rarely, a mass in the anterior upper mediastinum may be a primary mediastinal goiter. ¹ Even more rare is primary carcinoma in the ectopic mediastinal thyroid. ²

Case report

A 62-year-old woman was referred to Tampere University Hospital in 1993 because of a palpable pulsating tumor in the sternum. The patient was free of symptoms and in good general condition. Eight years earlier she had been operated on for a benign follicular goiter and 6 years earlier she had had a benign gastric ulcer.

Clinical examination revealed a mass in the middle portion of the sternum with a clear pulsation. Palpation of the neck demonstrated a pretracheal thyroid of normal size without abnormal nodules. Doppler examination demonstrated a strong whizzing sound in the tumor during systole. The chest x-ray film showed a weak soft tissue expansion behind the sternum (Fig. 1). A strongly vascularized tumor or arteriovenous fistula was suspected and angiography was performed. The angiogram revealed a vascular tumor behind the sternum with vascular supply from both internal thoracic arteries (Fig. 2). The vascular supply of the tumor was embolized with platinum coils. The size of the tumor decreased slightly and the pulsation disappeared. The tumor was believed to be possible hemangioma and an operation was considered. In the interval before the operation, the pulsation reappeared and the embolization was repeated together with direct percutaneous injection of 5 ml of absolute ethanol. Before the sclerotherapy, a sample was taken by fine needle aspiration, which revealed atypical cells with a mild suggestion of malignancy.

View larger version (122K): [in this window] [in a new window]   Fig. 1. Chest x-ray film demonstrates a weak soft tissue expansion, which was found to be an ectopic thyroid carcinoma, behind the sternum. Note the coils after embolization.

View larger version (210K): [in this window] [in a new window]   Fig. 2. Angiogram demonstrates the rich vascular supply of the tumor from internal thoracic arteries.

Final histologic study showed a pure follicular growth pattern, but locally there were slightly enlarged nuclei, crowded and overlapping and having a groundglass appearance, some of them with nuclear grooves. All of these features are consistent with papillary thyroid carcinoma. The tumor was considered to be a possible metastasis from a thyroid carcinoma. The histologic specimen of the previous thyroid tumor was reevaluated, but the pathologic diagnosis remained benign follicular adenomatous hyperplasia.

Total thyroidectomy was performed. Preoperative ultrasonography did not demonstrate any thyroid disease. There were no diseased nodules in the thyroid or in the nodular regions between the carotid vessels. There were no connections from the thyroid isthmus or lower poles to the upper part of the mediastinum. The whole thyroid gland weighed only 12 gm. Final histologic study did not demonstrate any neoplastic signs. The patient has recovered uneventfully from both operations. The postoperative scintiscan with radiolabeled iodine demonstrated minor accumulation of activity in the lower part of the mediastinum, but not in the neck.

Discussion

During embryogenesis, the thyroid gland develops together with the parathyroid and thymus from the primordial pharynx and its pouches. According to the time of the disturbance during embryogenesis, ectopic thyroid may develop at various sites from the base of the tongue to the thyroglossal duct. ³ The genesis of the thyroid gland also is related to the genesis of the heart. If contact with the heart is missed, a lingual thyroid may develop. If the contact is too close, intracardiac thyroid ectopy may develop. ⁴ The most common site for ectopic thyroid is the tongue, with thyroid tissue being microscopically detected in up to 10% of autopsies.

Mediastinal goiter is not uncommon, comprising about 15% of all goiters. However, in more than 99% of cases the mediastinal goiter is secondary, receiving its blood supply from thyroid arteries. ¹ A primary mediastinal thyroid, as in the present case, receives its blood supply from thoracic vessels, necessitating a thoracic approach during the operation. Ectopic mediastinal thyroid tissue is usually not alarming, but especially after pretracheal thyroidectomy it may become symptomatic. ⁵ The current patient had previously undergone thyroid resection, and that might have stimulated the growth of the ectopic mediastinal thyroid. However, she was free of symptoms, whereas more than half of patients with mediastinal goiters have symptoms.

In the present patient the mediastinal mass was a thyroid carcinoma. In patients with normal pretracheal thyroid it is difficult to distinguish with certainty between metastasis and primary ectopic carcinoma. However, careful examination of the pretracheal thyroidectomy specimen, in addition to angiographic finding, excluded the possibility of metastasis in the mediastinum. Instead, the tumor was a primary carcinoma of ectopic mediastinal thyroid. Primary ectopic thyroid carcinoma has previously been observed rarely. ²

Ectopic mediastinal thyroid and even primary thyroid carcinoma should be kept in mind when examining a patient with a mass in the upper anterior part of the mediastinum, even if the patient has a normal pretracheal thyroid gland.

Footnotes

From the Departments of Thoracic and General Surgery,^a Pathology,^b Radiology,^c and Medicine,^d Tampere University Hospital, Tampere Medical School, Tampere University, Tampere, Finland.

J THORAC CARDIOVASC SURG 1996;112:833-5

References

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3. Larochelle D, Arcand P, Belzile M, Gagnon NB. Ectopic thyroid tissue—a review of the literature. J Otolaryngol 1979;8:523-30.[Medline]
   
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5. Randolph J, Grunt JA, Vawter GF. The medical and surgical aspects of intratracheal goiter. N Engl J Med 1963;268:457-61.
   

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