What is the management approach for substernal thyroid nodules?

Management of Substernal Thyroid Nodules

For substernal thyroid nodules, CT imaging with contrast is essential for initial evaluation to assess the degree of retrosternal extension and tracheal compression, followed by surgical management for symptomatic or malignant lesions, with thermal ablation reserved as an alternative for benign nodules in patients who refuse or cannot tolerate surgery. 1

Diagnostic Evaluation

Imaging Strategy

• CT neck with contrast is the preferred imaging modality for substernal thyroid nodules, as it is superior to ultrasound for visualizing retrosternal extension, defining tracheal compression severity, and surgical planning 2, 1
• Ultrasound serves as the first-line modality for initial thyroid nodule detection but has significant limitations in assessing substernal components 1
• CT imaging should be performed for all fixed, bulky, or substernal lesions before treatment decisions 2

Pathological Confirmation

• Fine-needle aspiration biopsy (FNAB) remains the preferred method for cytological diagnosis of thyroid nodules, including those with substernal extension 2, 3
• All patients being considered for thermal ablation must undergo puncture biopsy to confirm pathological diagnosis before treatment 2
• Core needle biopsy (CNB) should be reserved for cases where FNAB is nondiagnostic, as CNB carries higher hemorrhage risk 2

Clinical Assessment

• Evaluate specifically for obstructive symptoms including dyspnea, orthopnea, obstructive sleep apnea, dysphagia, and dysphonia—all related to mass effect on the trachea or esophagus 1
• Assess vocal cord mobility using ultrasound, mirror indirect laryngoscopy, or fiberoptic laryngoscopy, particularly when planning surgical intervention 2
• Perform cervical lymph node evaluation by ultrasound when thyroid nodules are identified 2

Treatment Approach

Surgical Management (Primary Treatment)

Surgery is indicated for:

• Nodules causing significant compression symptoms 1
• Suspected or confirmed malignancy 1
• Progressive growth with increasing symptoms 1
• Retrosternal extension increases surgical complexity and complication risk, making preoperative CT imaging essential for operative planning 1

Thermal Ablation (Alternative Treatment)

Thermal ablation may be considered for benign substernal nodules when:

• The patient has medical contraindications to surgery 2, 1
• The patient refuses surgical intervention 2, 1
• The nodule causes compression symptoms but surgery is not feasible 1

Technical considerations for thermal ablation:

• US-CT fusion imaging with virtual needle tracking (VT) system improves feasibility and safety for large substernal nodules 4
• This technique achieved 100% feasibility and technical success in treating substernal nodules with mean volume 26.8 mL 4
• Volume reduction of 50% or greater was achieved in 93% of cases at 12-month follow-up, with mean volume reduction of 68.7% 4
• Minor complications occurred in 6.6% of cases with no major complications reported 4

Conservative Management

• For asymptomatic benign nodules without suspicious features, observation with regular monitoring is appropriate 3, 5
• Levothyroxine suppressive therapy is not recommended for benign thyroid nodules 3

Follow-Up Protocol

Post-Surgical Follow-Up

• Initial follow-up at one month after surgery 1
• Subsequent assessments at 3,6, and 12 months during the first year 1

Post-Ablation Follow-Up

• Immediate post-ablation assessment with contrast-enhanced ultrasound (CEUS) to evaluate completeness of ablation 2, 1
• Follow-up schedule similar to surgical patients: 1,3,6, and 12 months 1

Observation Protocol

• For benign nodules under surveillance, annual follow-up with thyroid and neck ultrasound to assess nodule size and characteristics 1

Critical Pitfalls and Complications

Anatomical Complications

• Compression of vital structures is the primary concern: tracheal compression leading to respiratory distress, esophageal compression causing dysphagia, and vascular compression affecting venous return 1
• Retrosternal extension significantly increases surgical complexity and potential for complications 1

Surgical Complications

• Voice changes, bleeding, hematoma, and nerve injuries are potential surgical complications 1
• Thorough preoperative vocal cord assessment helps identify baseline function and plan surgical approach 2

Thermal Ablation Limitations

• Cannot be used for diffuse sclerosing papillary carcinoma or malignancies other than papillary thyroid carcinoma 2
• Requires careful patient selection and should only be performed in experienced centers 2