Primary Intrathoracic Ectopic Thyroid Presenting With Superior Vena Cava Syndrome and Hoarseness: A Surgical Case Report

ABSTRACT

Primary intrathoracic ectopic thyroid is a rare entity that may present with compressive symptoms, including superior vena cava syndrome and hoarseness. Accurate radiologic evaluation and histopathologic confirmation are essential for diagnosis. Surgical resection provides definitive treatment and can result in significant symptomatic improvement and excellent clinical outcomes.

1. Introduction

The thyroid gland originates from the fusion of the median and lateral thyroid anlagen [1]. The median anlage develops during the second week of gestation, and as the tissue descends toward the heart, two diverticula form the thyroglossal duct connecting the two lobes [2]. This duct links the lobes to the base of the tongue and typically disappears during descent [3]. Around the fifth week of embryonic development, fusion of the lateral anlagen with the median anlage occurs, and by the seventh week, the gland reaches its final location anterior to the trachea [4].

Ectopic thyroid tissue can occur anywhere from the base of the skull to the mediastinum, although it is extremely rare in the latter location [5]. The term “intrathoracic goiter” (ITG) applies to thyroid tissue that resides within the thoracic cavity. ITGs are typically classified into:‐ Secondary ITGs, which descend from the cervical gland into the chest while maintaining vascular continuity and ‐ Primary ITGs, which are completely separate from the cervical thyroid and are vascularized exclusively by intrathoracic vessels [6]. This distinction is crucial, as primary ITGs may go unnoticed until they produce compressive symptoms.

Primary ITGs are usually found in the anterior superior mediastinum and contain normal thyroid histology [2]. They represent < 1% of all intrathoracic goiters [6]. Multiple terminologies—such as substernal, retrosternal, and mediastinal goiters—are used interchangeably. The most accepted definition, as proposed by Katlic et al., states that an intrathoracic goiter is present when more than 50% of the thyroid mass lies below the thoracic inlet [7, 8].

Clinical presentation varies, but symptoms are typically due to mechanical compression, including neck fullness, dysphagia, dyspnea, and superior vena cava syndrome (SVCS). Less commonly, patients may present with hoarseness or Horner's syndrome. Our patient presented with a rare combination of symptoms, including SVCS and hoarseness, due to a primary ITG [9].

Surgical resection is the treatment of choice for symptomatic ITGs, particularly when airway compression is present [10].

Primary intrathoracic goiter (ITG) is an uncommon clinical entity accounting for < 1% of intrathoracic goiters. Although compressive symptoms such as dyspnea and dysphagia are frequently reported, simultaneous presentation with superior vena cava syndrome (SVCS) and hoarseness is extremely rare. Previous reports in the literature have primarily focused on secondary ITGs, while primary ITGs with distinct intrathoracic vascular supply remain sparsely documented. Herein, we present a rare case of primary intrathoracic ectopic thyroid presenting simultaneously with superior vena cava syndrome and hoarseness. This uncommon clinical presentation, together with the lesion's independent intrathoracic vascular supply, highlights important diagnostic and surgical challenges.

2. Case History and Examination

A 67‐year‐old man presented with facial puffiness, neck swelling, and prominent chest wall and neck veins. He also reported progressive dyspnea and hoarseness at the time of admission. There was no history of weight loss, fever, night sweats, or smoking. His medical history was significant for hyperthyroidism treated with radioactive iodine therapy 10 years earlier, after which he had been receiving levothyroxine 100 μg daily. Physical examination demonstrated features suggestive of superior vena cava obstruction, including facial edema and dilated superficial veins over the neck and chest wall. Laboratory investigations, including thyroid function tests, liver function tests, and renal profile, were within normal limits, and the patient was biochemically euthyroid while receiving levothyroxine replacement therapy.

3. Methods

3.1. Differential Diagnosis

The differential diagnosis of an anterior mediastinal mass in this patient included thymoma, lymphoma, germ cell tumor, metastatic mediastinal disease, and ectopic thyroid tissue.

3.2. Investigations

A chest radiograph demonstrated a large right‐sided mediastinal opacity (Figure 1A,B). Contrast‐enhanced computed tomography (CT) of the chest revealed a massive right anterior mediastinal mass with heterogeneous enhancement, coarse calcifications, marked compression of the superior vena cava (SVC), and tracheal deviation (Figure 2A,B). The lesion appeared completely separate from the remnant cervical thyroid tissue, raising suspicion for a primary intrathoracic ectopic thyroid. Transthoracic needle biopsy confirmed the thyroid origin of the lesion.

FIGURE 1.

Preoperative and postoperative chest radiographs. (A) Preoperative chest radiograph demonstrating a large right‐sided mediastinal opacity (arrow) caused by the intrathoracic ectopic thyroid. (B) Postoperative chest radiograph showing complete removal of the mediastinal mass with resolution of mediastinal widening and improvement of tracheal deviation.

FIGURE 2.

Contrast‐enhanced chest computed tomography (CT) images. (A) Axial contrast‐enhanced CT image demonstrating a large anterior mediastinal mass (arrow) consistent with primary intrathoracic ectopic thyroid, causing compression of the superior vena cava (SVC) and tracheal deviation. (B) Coronal contrast‐enhanced CT image showing the extent of the ectopic thyroid mass (arrow) and its relationship to adjacent mediastinal structures, including compression of the SVC and displacement of the trachea.

3.3. Treatment

Given the severity of venous congestion, airway compression, and the large right‐sided mediastinal location of the lesion, surgical resection was planned. A right posterolateral thoracotomy through the fourth intercostal space was performed to provide optimal exposure and vascular control. Intraoperatively, a large intrathoracic mass occupying the anterior mediastinum was identified. The lesion compressed the superior vena cava, the right brachiocephalic vein, the trachea, and the right upper lobe of the lung. No continuity with the cervical thyroid gland was observed, and the mass received its blood supply exclusively from branches arising from the intrathoracic aorta, confirming the diagnosis of a primary intrathoracic ectopic thyroid. Complete excision was achieved without injury to the surrounding mediastinal structures. Gross examination revealed a large encapsulated mass (Figure 3). The patient was extubated in the operating room and transferred to the intensive care unit. His postoperative recovery was uneventful, and he was discharged on postoperative day five.

FIGURE 3.

Macroscopic view of the resected intrathoracic mass. (A) External surface showing a well‐encapsulated lesion. (B) Rotated specimen revealing smooth borders. (C) Cut surface displaying uniform brown tissue consistent with benign thyroid parenchyma.

4. Conclusion and Results

4.1. Outcome and Follow‐Up

Histopathological examination demonstrated benign thyroid follicular architecture without evidence of malignancy (Figure 4A,B). The postoperative course was uneventful, and the patient was discharged on postoperative day five.

FIGURE 4.

Histopathological examination of the resected mediastinal mass demonstrating benign thyroid tissue composed of variably sized colloid‐filled follicles lined by cuboidal follicular epithelium, consistent with ectopic thyroid tissue (hematoxylin and eosin stain). (A) Low‐power view showing thyroid follicles of varying sizes (scale bar = 100 μm). (B) Higher‐power view demonstrating benign follicular architecture with colloid‐filled follicles and cuboidal epithelial lining (scale bar = 50 μm).

At the 2‐month follow‐up visit, symptoms related to mediastinal compression, including facial edema, venous congestion, and dyspnea, had completely resolved. Postoperative chest radiography confirmed complete removal of the mediastinal mass with restoration of normal mediastinal contours. Mild residual hoarseness persisted, likely reflecting preoperative recurrent laryngeal nerve compression; however, the patient's overall clinical condition had markedly improved, with no evidence of recurrence or postoperative complications.

5. Discussion

Ectopic thyroid tissue (ETT) is a rare congenital anomaly with an estimated incidence of 1 in 100,000–300,000 individuals in the general population, and a slightly higher prevalence among patients with thyroid disorders. Most ectopic thyroids are located along the embryologic descent pathway, typically in the lingual or subhyoid regions, whereas intrathoracic localization is exceedingly uncommon, accounting for < 1% of reported cases [2, 3].

Primary intrathoracic goiters (ITGs) are characterized by complete separation from the cervical thyroid gland and an exclusive vascular supply arising from intrathoracic vessels [2, 11]. This distinction carries significant surgical implications, as cervical approaches are usually inadequate, and thoracotomy or sternotomy is often required for complete excision [3, 6]. Our patient exhibited a classic presentation of a primary ITG, confirmed intraoperatively by the absence of continuity with the cervical thyroid and the presence of direct vascularization from the intrathoracic aorta.

The clinical manifestations of ITG vary and are primarily attributable to compression of adjacent mediastinal structures. Common symptoms include dyspnea, dysphagia, and neck fullness, whereas superior vena cava syndrome (SVCS) and hoarseness are much less frequently encountered [6]. The simultaneous occurrence of SVCS and persistent hoarseness, as seen in our patient, is infrequent and highlights the broad spectrum of compressive effects caused by ITG. Although previous studies have described hoarseness secondary to recurrent laryngeal nerve involvement [12], the co‐existence of venous obstruction has been scarcely documented.

Radiologic imaging, particularly contrast‐enhanced computed tomography (CT), remains the cornerstone of diagnosis, as it provides essential information regarding the extent of compression, the relationship to vital mediastinal structures, and the separation from cervical thyroid tissue. Functional imaging and histopathological confirmation may support diagnosis, although needle biopsy of hypervascular mediastinal lesions carries a risk of hemorrhage [1]. In our case, preoperative CT and transthoracic needle biopsy confirmed the thyroid origin, which facilitated surgical planning.

Surgical excision remains the definitive treatment for symptomatic ITG, as non‐surgical management carries risks of progressive airway obstruction, venous compression, and, rarely, malignant transformation. The choice of surgical approach depends on the size, location, and vascular supply of the mass: while cervical thyroidectomy suffices for most secondary ITGs, thoracotomy or sternotomy is typically required for primary lesions [6, 13]. The surgical approach for intrathoracic goiter depends primarily on lesion location, vascular anatomy, and mediastinal extension. While most secondary intrathoracic goiters can be approached through cervical incision or sternotomy, primary lesions with independent intrathoracic vascular supply frequently require thoracotomy. In our patient, the right‐sided mediastinal position favored a posterolateral thoracotomy approach. Our patient underwent posterolateral thoracotomy with complete resection, resulting in full resolution of venous congestion and dyspnea. Mild residual hoarseness persisted at follow‐up, likely due to preoperative compression of the recurrent laryngeal nerve. Potential complications of ITG surgery include recurrent laryngeal nerve injury, tracheomalacia, hemorrhage, and hypocalcemia [14, 15]. The absence of major complications in our patient supports the safety and efficacy of thoracotomy when performed in appropriately selected cases. Nevertheless, persistent hoarseness underscores the importance of early diagnosis and timely surgical intervention before irreversible nerve injury occurs.

In summary, this case emphasizes that primary ITG should be considered in the differential diagnosis of mediastinal masses in thyroid patients without palpable cervical goiter. The rare co‐presentation of SVCS and hoarseness highlights the need for high clinical suspicion. Careful radiological assessment is essential for accurate diagnosis, surgical planning, and prevention of complications.

This case highlights the importance of considering primary intrathoracic ectopic thyroid in the differential diagnosis of anterior mediastinal masses presenting with compressive symptoms. Accurate preoperative imaging, awareness of independent intrathoracic vascular supply, and complete surgical excision are essential for achieving favorable outcomes.

Author Contributions

Mohammad Taghi Ashoobi: conceptualization, investigation, methodology, resources, supervision, writing – review and editing. Manouchehr Aghajanzadeh: conceptualization, investigation, methodology, resources, supervision, writing – review and editing. Mohaya Farzin: conceptualization, data curation, formal analysis, methodology, project administration, writing – original draft, writing – review and editing. Arselane Dadashi: data curation, investigation, writing – review and editing. Omid Mosaffaee Rad: data curation, investigation, validation, writing – review and editing. Ali Alavi Foumani: data curation, investigation, writing – review and editing. Azita Tangestaninejad: data curation, investigation, methodology, writing – review and editing. Ali Asghar Fakhrmousavi: data curation, investigation, writing – review and editing. Zahra Sadin: data curation, funding acquisition, writing – review and editing.

Funding

The authors have nothing to report.

Ethics Statement

This study was approved by the Ethics Committee of Guilan University of Medical Sciences (IR.GUMS.RES.1404.132).

Consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.