The “forgotten” goiter after total thyroidectomy

Abstract

INTRODUCTION

“Forgotten” goiter is an extremely rare disease which is defined as a mediastinal thyroid mass found after total thyroidectomy.

PRESENTATION OF CASE

We report two cases with forgotten goiter. One underwent total thyroidectomy due to thyroid papillary cancer and TSH level was in normal range one month after surgery. The thyroid scintigraphy scan revealed mediastinal thyroid mass. The second case underwent total thyroidectomy due to Graves’ disease and TSH level was low after surgery. At postoperative seventh year, patients were admitted to our Endocrinology Division due to persistent hyperthyroidism and CT scan revealed forgotten thyroid at mediastinum. Both patients underwent median sternotomy and mass excision, there was no morbidity detected after second surgical procedures.

DISCUSSION

In the majority of cases forgotten goiter is the consequence of the incomplete removal of a plunging goiter. Although in some cases, it may be attributed to a concomitant, unrecognized mediastinal goiter which is not connected to the thyroid with a thin fibrous band or vessels. Absence of signs like mediastinal mass or tracheal deviation in preoperative chest X-ray do not excluded the substernal goiter.

CONCLUSION

Retrosternal goiter should be suspected if the lower poles could not be palpated on physical examination and when postoperative TSH levels remained unchanged.

1. Introduction

“Forgotten thyroid” is retrosternal portion of thyroid gland which is connected to cervical portion of thyroid with or without a thin fibrous band or vascular structure and not realized or forgotten during total thyroidectomy.¹ In some cases, cervical portion of thyroid gland goes beyond, with stretched neck to the superior thoracic strait for at least 3 cm that called “retrosternal goiter”.^2–4 Therefore, in some cases, an autonomous intrathoracic goiter (AIG) is located in the thorax or, more precisely, in the mediastinum. This thyroid segment is not a metastasis of thyroid cancer, it has no parenchymatous or vascular connections with the cervical part of thyroid gland. AIG is basically caused by an abnormal embryonic progression of the thyroid gland and it must be distinguished from migratory goiters in partially resected or forgotten thyroid gland after cervicotomy.⁵

Here, in this manuscript we report two cases that previously underwent a total thyroidectomy with “forgotten thyroid” in mediastinum.

2. Case-1

The patient was a 37-year-old woman, who underwent total thyroidectomy for previously detected thyroid papillary carcinoma at our hospital. She had normal thyroid function tests and TSH level before the first surgery. There was no trachea compression or deviation in chest X-ray preoperatively. No thyroid scintigraphy scan before operation because of normal levels of thyroid hormones. She had 1.5 cm in widest diameter thyroid papillary cancer without a thyroid capsule involvement. She was planned to have radioactive iodine (RAI) treatment, but TSH level was not increased (5 mIU/L) at the 4th postoperative week without a replacement levothyroxine therapy. An ultrasonography (USG) is obtained, but did not show any residual tissue. On thyroid scintigraphy, there was a mediastinal thyroid focus detected (Fig. 1). A computed tomography scan showed a 4 cm × 4 cm in diameter midline mass lying retrosternally (Fig. 2). The mass is removed through a mini-sternotomy (Fig. 3). Pathology revealed no papillary cancer involvement. There was no postoperative morbidity detected after sternotomy procedure.

Fig. 1.

Mediastinal activity in scintigraphy scan.

Fig. 2.

Anterior mediastinal mass.

Fig. 3.

Removed thyroid tissue.

3. Case-2

The second patient was a 72-year-old male. He had tachycardia, breathlessness due to high thyroid hormone levels. There was no thyroid nodules on thyroid USG. He was on anti-thyroid treatment and his thyroid hormones levels and TSH level were in normal ranges before surgery. He underwent total thyroidectomy because of Graves’ disease in private hospital in Istanbul. Preoperative chest X-ray was normal, no signs of trachea compression or deviation. After total thyroidectomy, his symptoms were persisted. Free T3 level was 7.2 pmol/L and free T4 levels was 24.3 pmol/L and TSH level was 0.1 mIU/L. Hyperthyroidism was persisted postoperatively. He was put on anti-thyroid medication again. USG did not show any residual thyroid tissue. After surgery, the patients was received two times RAI therapy, but had to continue to take anti-thyroid medication, because of persistent hyperthyroidism. After 7 years, he admitted to our hospital, Internal Medicine Department, Endocrinology Division. A neck and thorax computed tomography scan was obtained. There was a large posterior mediastinal mass visible on the right side 13 cm × 5 cm in diameter (Fig. 4). The scintigraphy showed an activity on this mass lesion. The mass was removed with a median sternotomy (Fig. 5) and the pathology of the specimen resulted as 6 mm papillary carcinoma. There was no postoperative morbidity detected after sternotomy procedure.

Fig. 4.

Posterior mediastinal mass.

Fig. 5.

Removed posterior mediastinal mass.

4. Discussion

“Forgotten” goiter is an extremely rare disease which is defined as a mediastinal thyroid mass found after total thyroidectomy.^2,6 In the literature, it is known that forgotten goiter is usually the consequence of the incomplete removal of a plunging goiter, and moreover, sometimes it may be attributed to a concomitant, unrecognized mediastinal goiter which is not connected to the thyroid (AIG).^5,7

A retrosternal goiter (RG) is commonly defined as a goiter having most of its mass in the mediastinum. The definition of substernal goiter is not uniform and varies among authors. Retrosternal goiter incidence rates range between 0.2% and 45% of all goiters, depending on the definition used. About 20–40% of retrosternal goiters are symptomatic. Remaining of RGs is discovered as an incidental finding on a radiographic or clinical examination. The routine chest radiographs seldom do not show a mediastinal mass. RG should be suspected if the lower poles could not be palpated on physical examination.^8–11 In our both cases, there was no symptoms due to remaining thyroid mass in mediastinum. The residual goiter has the same clinical presentation as a regular intrathoracic goiter in both patients. In the first case, we did not palpate any mass beneath the thyroid gland extending to mediastinum. In the second case, we did not know that the intraoperative physical examination, due to the previous operation at a different hospital.

In some instances mediastinal portion of RGs is connected to the cervical part with a thin fibrous band, that is why the mediastinal extension is leaved out during cervical exploration.^1,2 Absence of signs like mediastinal mass or tracheal deviation in preoperative chest X-ray causes to leave these cases out.

Forgotten goiter is a rare pathology which can be prevented if particular attention is paid to preoperative imaging and intraoperative management during the first operation. However surgical treatment for forgotten goiter, when performed in specialized centers, is associated with low morbidity.

5. Conclusion

Forgotten goiter should strongly be suspected when postoperative TSH levels remained unchanged.

Conflict of interest statement

None.

Funding

None.

Ethical approval

We have obtained written consent from the patient for publication of this case report and accompanying images.

Author contributions

Alper Şahbaz and Nihat Aksakal contributed to study design. Feyyaz Onuray and Kasım Çağlayan contributed to data collections and Yeşim Erbil contributed to writing.