Retrosternal Goitre

Classification — primary vs secondary

Pathogenesis

The thyroid gland develops from endoderm of the floor of the pharynx and descends to its normal position anterior to the trachea. Goitrous enlargement — driven by iodine deficiency, autoimmune thyroiditis, or nodular hyperplasia — may extend inferiorly into the mediastinum. Gravity, negative intrathoracic pressure during inspiration, and the anatomical narrowing of the thoracic inlet all contribute to the downward displacement. The gland typically lies anterior to the trachea in the prevascular compartment, but may deviate to lie posterolaterally or even posterior to the oesophagus (rare).

Clinical features

Retrosternal goitre is more common in women (M:F = 1:3–4) and typically presents in the 5th–7th decades. Many are incidentally discovered on chest imaging. When symptomatic:

• Tracheal compression: dyspnoea, stridor, orthopnoea (worsens lying flat — trachea compressed), positional wheeze
• Oesophageal compression: dysphagia, regurgitation
• Venous compression: facial flushing, arm swelling, dilated neck veins; Pemberton's sign — raising both arms above the head for 1 minute causes facial congestion, cyanosis, and stridor as the goitre is pushed upward into the thoracic inlet
• Recurrent laryngeal nerve: hoarseness (rare without malignancy)
• Horner's syndrome: cervical sympathetic chain compression (rare)

Investigations

• CT chest (with contrast): investigation of choice — delineates extent, tracheal deviation and compression, relationship to great vessels, calcification, and any malignant features
• Thyroid function tests: TSH, free T4, free T3 — most are euthyroid
• Thyroid scintigraphy (Tc-99m or I-123): confirms thyroid tissue in the mediastinal mass and identifies autonomous nodules
• FNAC: if malignancy suspected — CT-guided for intrathoracic component
• Pulmonary function tests: flow-volume loop — fixed or variable extrathoracic obstruction pattern; assesses functional impairment
• Indirect laryngoscopy: vocal cord mobility before surgery — document any pre-existing RLN palsy

Treatment

Surgery is indicated for all symptomatic retrosternal goitres and for asymptomatic goitres with significant tracheal compression (>50% luminal narrowing) or suspected malignancy. The longer surgery is deferred, the more technically demanding it becomes as the gland enlarges and fibroses to mediastinal structures.

Cervical approach (standard)

The vast majority of secondary retrosternal goitres (80–95%) can be safely removed through a standard cervical incision. The mediastinal component is delivered into the neck by: (1) systematic ligation of all cervical vessels to the gland; (2) finger dissection to separate it from mediastinal attachments; (3) upward delivery by sustained gentle traction combined with compression from below by an assistant's finger in the sternal notch.

Indications for sternotomy

• Primary mediastinal goitre (no cervical connection)
• Posterior mediastinal goitre (behind the aortic arch or oesophagus)
• Malignant goitre with mediastinal invasion
• Failure to deliver the goitre via cervical route
• Significant bleeding from mediastinal vessels inaccessible through the neck
• Recurrent goitre after previous cervical surgery — distorted anatomy

Tracheomalacia — softening of the tracheal rings from chronic compression by the goitre — may cause tracheal collapse after goitre removal. Suspect if the trachea appeared markedly narrowed or deviated on pre-operative CT. Have a plan for post-operative airway support, and involve ENT/thoracic surgery if malacia is anticipated.