What is the next step for a 1 cm solid hypoechoic thyroid nodule classified as Thyroid Imaging Reporting and Data System (TI-RADS) 3 or 4?

Management of 1 cm Solid Hypoechoic Thyroid Nodule (TR3 or TR4)

For a 1 cm solid hypoechoic thyroid nodule classified as TI-RADS 4, proceed with ultrasound-guided fine-needle aspiration (FNA) biopsy; for TI-RADS 3, surveillance with follow-up ultrasound is appropriate unless additional high-risk clinical features are present. 1, 2

Risk Stratification Based on TI-RADS Category

TI-RADS 4 (Moderately Suspicious)

• FNA is indicated for nodules ≥1.0 cm classified as TI-RADS 4, as this represents an intermediate-to-high suspicion pattern where the combination of solid composition and hypoechoic appearance warrants tissue diagnosis 1, 2, 3
• The malignancy rate for TI-RADS 4 nodules ranges from 12-34% depending on subcategory (4A vs 4B), making cytological evaluation essential at this size threshold 4
• Ultrasound-guided FNA is the gold standard diagnostic method, offering accuracy, cost-effectiveness, and safety 2

TI-RADS 3 (Mildly Suspicious)

• For TI-RADS 3 nodules at 1.0 cm, surveillance is generally recommended rather than immediate FNA, as current guidelines typically recommend FNA for TR3 nodules only when they reach 1.5 cm 1, 5
• The malignancy rate for TI-RADS 3 nodules is approximately 2.87%, which is considered low risk 4
• However, if the nodule has additional concerning features (subcapsular location, suspicious lymph nodes, rapid growth, or strong family history), FNA should be considered despite the 1.0 cm size 1

Critical Clinical Context That Modifies Management

High-Risk Features That Lower FNA Threshold

• History of head and neck irradiation 1
• Positive family history of thyroid cancer 1
• Presence of suspicious cervical lymphadenopathy 1
• Subcapsular location of the nodule 1
• Additional suspicious ultrasound features: microcalcifications, irregular borders, absence of peripheral halo, or abnormal blood flow 1, 2

Size Considerations

• The 1.0 cm threshold is critical in current guidelines, as nodules <1 cm are generally recommended for surveillance unless high-risk features are present 1
• Non-subcapsular thyroid nodules <1 cm (cT1a cN0) should not undergo FNA even if high-risk by TI-RADS, according to recent consensus 1

Procedural Approach for FNA (When Indicated)

Technical Execution

• Ultrasound guidance is mandatory for accurate sampling and to minimize inadequate specimens 2
• FNA remains the most accurate and cost-effective method for preoperative diagnosis of thyroid malignancy 1

Expected Cytological Outcomes

• Papillary thyroid carcinoma is well-detected on FNA samples 1
• Follicular neoplasms may yield indeterminate results requiring surgical excision for definitive diagnosis 1
• If initial FNA is inadequate, repeat the procedure 1, 6

Adjunctive Testing

• Consider serum calcitonin measurement as part of the diagnostic evaluation, as it has higher sensitivity than FNA for detecting medullary thyroid cancer (5-7% of thyroid cancers) 1, 6
• Molecular testing (BRAF, RAS, RET/PTC, PAX8/PPARγ) may be considered for indeterminate cytology results 6, 2

Surveillance Protocol (When FNA Not Performed)

For TI-RADS 3 at 1.0 cm

• Follow-up ultrasound in 6-12 months to assess for growth or development of additional suspicious features 7, 5
• If the nodule grows or develops concerning features, proceed to FNA 7

Pitfalls to Avoid

• Do not rely on thyroid function tests (TSH, T3, T4) for malignancy assessment, as most thyroid cancers present with normal thyroid function 1, 6
• Avoid performing FNA on nodules <1 cm without high-risk features, as this leads to overdiagnosis and overtreatment of clinically insignificant cancers 1, 2
• The nondiagnostic rate for subcentimeter nodules is higher (7%) compared to larger nodules (3%), which should factor into decision-making 8

Key Divergence in Evidence

While older guidelines from 2009 recommend FNA for any nodule >1 cm with suspicious features 1, more recent 2025 guidance emphasizes that TI-RADS classification should guide FNA decisions, with size thresholds varying by risk category 1. This reflects evolving understanding that not all 1 cm nodules require biopsy, particularly those with lower suspicion patterns (TR3), to avoid unnecessary procedures while maintaining appropriate cancer detection rates.