Management of Thyroid Cysts
For thyroid cysts with <10% solid component, chemical ablation with ethanol is the preferred treatment, while cysts with ≥10% solid component should undergo thermal ablation techniques after confirming benign pathology via fine-needle aspiration biopsy. 1
Initial Diagnostic Approach
All thyroid cysts require pathological confirmation before definitive treatment:
- Fine-needle aspiration biopsy (FNAB) is mandatory for all thyroid nodules being considered for ablation therapy 1
- Cystic and cavernous nodules on ultrasound can undergo FNAB once, while other nodules require FNAB twice or in combination with core needle biopsy 1
- Ultrasound of the thyroid and central neck should be performed to characterize the lesion 1
- TSH measurement guides subsequent management decisions, though it does not directly diagnose malignancy 2
Critical caveat: Malignancy occurs in approximately 14% of cystic thyroid lesions, similar to the 23% rate in solid nodules 3. The malignancy rate is highest in male patients and nodules ≥4 cm 4. FNAB is slightly less reliable for cystic lesions compared to solid nodules, with sensitivities of 88% versus 100% respectively 3.
Treatment Algorithm Based on Cyst Composition
Purely Cystic or <10% Solid Component
Chemical ablation with ethanol is the first-line treatment:
- Ethanol ablation achieves cure rates of 82% compared to 48% with simple aspiration and saline flushing 5
- 64% of patients are cured after a single ethanol session versus 18% with saline alone 5
- The procedure involves subtotal aspiration, flushing with 99% ethanol, and subsequent complete fluid aspiration 5
- Treatment can be repeated up to three times if recurrence occurs (defined as cyst volume >1 mL) 5
- Ethanol ablation is particularly effective for simple cysts and complex cysts with solid component <20% 6
Predictors of treatment failure with ethanol:
- Higher number of previous aspirations decreases success rates 5
- Larger baseline cyst volume reduces cure probability 5
- Complex cysts with >20% solid component may have better outcomes with radiofrequency ablation 6
Cystic Nodules with ≥10% Solid Component
Thermal ablation is indicated after confirming benign pathology:
- Radiofrequency ablation (RFA), microwave ablation (MWA), laser ablation (LA), or high-intensity focused ultrasound (HIFU) are appropriate options 1
- Thermal ablation is recommended for nodules that cause compression symptoms, cosmetic concerns, anxiety, or nodules ≥2 cm that are gradually enlarging 1
- All patients must have benign pathology confirmed by biopsy before thermal ablation 1
Advantages of thermal ablation over surgery:
- No neck scar, shorter procedure time, outpatient treatment possible 1
- Preservation of thyroid function without lifelong medication in most cases 1
- Lower complication rates compared to traditional surgery 1
Indications for Surgical Excision
Surgery should be considered when:
- Malignant cytology is obtained (100% predictive of cancer) 3
- Cysts ≥4 cm in male patients (highest malignancy risk) 4
- Cysts not abolished by aspiration, particularly with indeterminate cytology 3
- Signs of local compression, invasion, or radiologic findings suggesting malignancy 4
- Severe bleeding tendency, severe cardiopulmonary insufficiency, or contralateral vocal cord paralysis (contraindications to ablation) 1
Post-Treatment Monitoring
- Monthly evaluations for 6 months after ethanol ablation to detect recurrence 5
- For thermal ablation patients requiring TSH suppression therapy, monitor TSH at 3,6, and 12 months during the first year, then every 6 months 2
- Ultrasound surveillance to assess volume reduction and detect complications 1
Common Complications and Management
Ethanol ablation complications:
- Moderate to severe pain occurs in 21% of patients (median duration 5 minutes) 5
- Transient dysphonia is rare but possible 5
- Serious side effects are uncommon 5
Thermal ablation complications: