Risk of Malignancy in a Multinodular Goiter: Report of Two Cases with a Literature Review

INTRODUCTION

Goiter is a common disease in Malaysia. Our hospital has had experience in variable types and sizes of goiters. However, subgroups of a multinodular goiter should be known. There are retrosternal, substernal, and intrathoracic goiters. Many classifications have been given for this, as approach to surgery differs. To treat a benign intrathoracic multinodular goiter with an intraoperative pathology report of micropapillary thyroid carcinoma can be challenging. We will discuss about two cases in keeping with this scenario.

CASE DESCRIPTION

DISCUSSION

Multinodular goiter refers to an enlarged thyroid gland with multiple nodules. This results from biosynthetic defects, iodine deficiency, autoimmune disease, or nodular diseases. Complications of untreated multinodular goiter can cause clinical symptoms such as dyspnea or dysphagia. Protuberance of goiters is usually easily noticed and are often treated medically or removed surgically. Lin and Chang reported that intrathoracic goiters account for 0.2–45% of all goiters and most commonly affect women in their sixth and seventh decades of life. The thoracic cavity provides some interior space; therefore, goiters located within can enlarge progressively without symptoms and grow to a considerable size.¹ Patients with a multinodular goiter require a careful evaluation for the risk of malignancy within the multiple nodules, selecting patients who require surgery, and planning an appropriate surgical approach to address the disease without an undue risk of complications. Morphological and molecular studies suggest a degree of polyclonal etiology. Multinodular goiters are sometimes familial and one study suggests linkage to a DNA mother as chromosome 14q.²

Haller first provided an anatomical description of the intrathoracic goiter in 1794, since then a number of names and descriptions such as retrosternal, substernal, retroclavicular, and intrathoracic goiter has been given. Intrathoracic goiter can be classified as “incomplete” or “complete”. The goiter is “incomplete” when a major portion in the neck is visible, with its lower pole being substernal, subclavicular, or intrathoracic. Conversely, “complete” or true is completely in the mediastinum. Thus, the uppermost part is barely palpable in the sternal notch.³ There is also primary, which are ectopic thyroid tissue detached from a cervical thyroid mass and is very rare (1%), or secondary, which is more common where a portion of the goiter extends retrosternal.

Although goiters are mostly thought to be benign, but this type of goiter has a risk for malignancy. For a thyroid gland to reach a sufficient size to pass into the mediastinum, the pathological processes involved must have been present for many years. It is therefore unsurprising that the vast majority of surgical specimens demonstrate a benign pathology. The rate of malignancy in reported surgical series, however, is low (6–21%). However, it is important to consider malignancy because it may significantly alter management.⁴

Micropapillary thyroid carcinoma is defined as a papillary carcinoma of the thyroid that is less than 10 mm in diameter. Merdad et al.⁵ summarized the latest thyroid nodule management guidelines published by the European Thyroid Association (ETA; 2006), British Thyroid Association (BTA; 2007), and American Thyroid Association (ATA; 2009). The management of micropapillary thyroid carcinoma are as shown in Table 1.

Simo et al. described a surgical approach for intrathoracic goiters. It poses significant intra and postoperative challenges. There are differences between total and hemithyroidectomy approach. Total thyroidectomy is indicated for bilateral thyroid gland enlargement. However, in patients with unilateral enlargement or posing a significant risk to the recurrent laryngeal nerve or parathyroid function, thyroid lobectomy is a perfectively acceptable option as the majority of goiters will be benign.⁴

The option of cervical and extracervical approach should be considered. Most commonly cervical approach is suitable for 95% of intrathoracic goiters. The extracervical approach would require sternotomy and moreover when an intrathoracic goiter is significantly located in the mediastinum, retrotracheal, or retroesophageal position, or if the intrathoracic component is significantly larger than the cervical one. The main indications for an extracervical approach therefore are a giant intrathoracic extension, recurrent goiters, presence of malignancy with an extrathyroidal extension, an extension posterior to trachea and esophagus, an extension between trachea and esophagus, Isolated mediastinal goiters, and intrathoracic goiters with a diameter greater than the diameter of the thoracic inlet.^1,2

According to British Thyroid Association for Management of Thyroid Cancer,⁶ surgery for micropapillary thyroid carcinoma with less than 10 mm in diameter can be treated adequately by thyroid lobectomy provided that:

• The tumour does not extend beyond the thyroid capsule
• There is no evidence of metastases
• There is no evidence of vascular invasion
• There is no evidence of multifocality
• There is no evidence of contralateral disease.

A subsequent treatment to consider for managing a micropapillary thyroid carcinoma is radio active iodine (RAI) and follow-up. As summarized by Merdad et al., RAI is not required if a complete surgery is done with a unifocal or multifocal margin of %3C;1 cm without an extrathyroidal extension with the staging of N0M0. From this, whether a decision for RAI is required is clear. There is no guideline regarding the years to do follow-up of patients with a micropapillary thyroid carcinoma; however, multiple studies have been conducted to detect the recurrence rate but it varies in duration.

Noguchi et al. stated that the diagnosis of a benign nodule shows a slightly better prognosis than a preoperative diagnosis of a malignant nodule and also a tumour size of 1–5 mm gives an improved recurrence-free survival rate when compared to a size of 6–10 mm.⁷

CONCLUSION

Both of our cases were incomplete intrathoracic multinodular goiters that apparently looked to be benign. A thyroidectomy was performed using the cervical approach and did not require a sternotomy. Despite a low risk of malignancy in such types of goiters, the possibility of a micropapillary carcinoma should be ruled out. In our cases, although the cytological examinations of the aspirated glands were negative for malignancy, intraoperative thyroid samples showed micropapillary carcinomas. In both patients, having complete surgery, no extrathyroidal extension, and a tumor diameter of <5 mm no RAI was required. Both of them did not require any further postoperative treatment and was reviewed in the clinic. Both patients are well during the follow-up and showed no evidence of recurrence.

REFERENCES

1. Lin YS, Chang HC. Giant intrathoracic goitre: a case report. OA Case Rep 2013 May 01;2(4):39.

2. Cohen JP. Substernal Goiters and Sternotomy. Laryngoscope 2009 Apr;119(4):683–688. DOI: 10.1002/lary.20102.

3. Asciak PP, Higgins K. Management of intrathoracic Goitre. Can J Surg 2008 Oct;51(5):E111–E112.

4. Simo R, Nixon I, et al. Surgery For Intrathoracic (Retrosternal) Goitres. Open Access Atlas Otolaryngol Head Neck Oper Surg;1–17.

5. Merdad M, Eskander A, et al. Current Management of Papillary Thyroid Microcarcinoma in Canada. J Otolaryngol Head Neck Surg 2014;43:32.

6. Association BT. Guidelines for the Management of Thyroid Cancer In: Physicians RCo.Great Britain: The Lavenham Press, Suffolk; 2007.

7. Noguchi S, Yamashita H, et al. Papillary Microcarcinoma. World J Surg 2008 May;32(5):747–753. DOI: 10.1007/s00268-007-9453-0.