What is the management approach for a patient with a cystic thyroid lesion containing siderophages (iron-containing macrophages)?

Management of Cystic Thyroid Lesion with Siderophages

A cystic thyroid lesion containing siderophages (hemosiderin-laden macrophages indicating prior hemorrhage into the nodule) should undergo fine-needle aspiration biopsy (FNAB) to confirm benign pathology, followed by either simple aspiration, ethanol ablation, or thermal ablation depending on the solid component percentage and recurrence pattern. 1

Initial Diagnostic Approach

All patients with thyroid nodules being considered for intervention must undergo puncture biopsy to confirm pathological diagnosis, with FNAB as the preferred method. 1 The presence of siderophages indicates prior hemorrhage into a cystic nodule, which is a common finding in benign thyroid lesions but does not exclude malignancy. 2

Key Diagnostic Steps:

• Perform FNAB as first-line diagnostic procedure to obtain cytological diagnosis per the Bethesda System for Reporting Thyroid Cytopathology. 1
• For cystic and cavernous nodules, FNAB should be performed at least once; other nodules require FNAB twice or in combination with core needle biopsy (CNB). 1
• Ultrasound evaluation should assess nodule size, composition (percentage of solid vs. cystic components), and presence of suspicious features. 1

Risk Stratification Considerations:

• Male sex and nodule size ≥4 cm are statistically significant predictors of malignancy in cystic lesions. 2
• When initial FNAB shows cystic change (fluid aspiration with numerous macrophages but scant follicular cells), nodules ≥4 cm must be reaspirated to rule out malignancy. 2
• The malignancy rate for incidental thyroid lesions is approximately 1.8%, while palpable/symptomatic lesions carry a 10.2% malignancy risk. 3

Treatment Algorithm Based on Nodule Characteristics

For Confirmed Benign Cystic Lesions:

The optimal treatment depends on the solid component percentage and patient symptoms: 4

Predominantly Cystic (<10% solid component):

• Chemical (ethanol) ablation is the preferred first-line treatment for cysts or cystic nodules with solid composition <10%. 1
• Ethanol ablation is at least as effective as radiofrequency ablation for simple cysts and complex cysts with solid component <20%. 4
• Simple aspiration is reasonable for initial management but has high recurrence rates; further aspirations are unlikely to be effective if fluid re-accumulates. 4

Complex Cystic Lesions (10-20% solid component):

• Thermal ablation is applicable to solid nodules or cystic nodules with solid composition ≥10% confirmed as benign by biopsy. 1
• Ethanol ablation remains a reasonable first-line option, though efficacy is inversely related to the percentage of solid component. 4

Complex Cystic Lesions (>20% solid component):

• Complex cysts with >20% solid component may have better long-term outcomes with radiofrequency ablation (RFA) over ethanol ablation. 4
• RFA salvage after ethanol ablation is possible and effective, especially for complex nodules with larger solid components. 4

Indications for Intervention:

Treatment is indicated when benign nodules meet any of the following criteria: 1

• Nodules causing clinical symptoms such as compression, cosmetic concerns, or anxiety
• Nodules with maximal diameter ≥2 cm that are gradually increasing in size
• Autonomously functioning thyroid nodules
• Recurrent nodules after chemical ablation

Important Caveats and Pitfalls

Cytology Limitations:

• In one study, 71% of malignancies in cystic nodules were not cytologically diagnosed on initial aspiration. 2 This underscores the importance of reaspiration for larger lesions and those with suspicious features.

Contraindications to Thermal Ablation:

• Patients with severe bleeding tendency should not undergo thermal ablation. 1
• Patients with severe cardiopulmonary insufficiency are contraindicated. 1

Follow-up Requirements:

• Patients should be informed of the advantages and limitations of thermal ablation, and informed consent must be obtained. 1
• Nodules classified as indeterminate on ultrasound require closer surveillance or surgical consideration. 3

When to Consider Surgery:

• Surgery should be considered for nodules ≥4 cm in males, nodules with malignant cytology on reaspiration, or those with radiologic findings of local invasion. 2
• Nodules that fail ablation therapy or demonstrate growth despite treatment warrant surgical evaluation. 1