What does Thyroid Imaging Reporting and Data System category 3 (TI‑RADS 3) indicate and what is the recommended management?

TI-RADS 3: Low-Risk Thyroid Nodules Requiring Surveillance, Not Immediate Biopsy

TI-RADS 3 thyroid nodules carry a malignancy risk of only 1.3–2.0% and should be managed with ultrasound surveillance rather than fine-needle aspiration, unless they reach ≥1.5 cm in size or high-risk clinical features are present. 1, 2, 3

Definition and Risk Stratification

TI-RADS 3 nodules are defined by the absence of suspicious ultrasound features—they lack microcalcifications, marked hypoechogenicity, irregular margins, taller-than-wide shape, or absence of peripheral halo. 2 These nodules represent a low-suspicion category with documented malignancy rates between 1.3% and 2.0% across validation studies. 2, 3

In a prospective study of 3,980 thyroid nodules, only 6 of 466 TI-RADS 3 nodules (1.3%) proved malignant, compared to 95.5% malignancy in TI-RADS 5 nodules. 2 A more recent 2025 study confirmed that 75% of TI-RADS 3 nodules are cytologically benign, with only 8 of 384 nodules (2.0%) ultimately diagnosed as carcinoma on surgical resection. 3

Recommended Management Algorithm

Initial Assessment

• Measure TSH levels to assess thyroid function before initiating surveillance. 1
• Perform high-resolution ultrasound to document baseline nodule characteristics, including size, composition (solid vs. cystic), echogenicity, margins, and vascularity. 1
• Assess for suspicious features that might warrant reclassification to TI-RADS 4 or 5, such as microcalcifications, marked hypoechogenicity, irregular margins, absence of peripheral halo, or central hypervascularity. 1

Size-Based Decision Making

• For nodules <1.5 cm: Proceed with ultrasound surveillance at 12–24 month intervals. 4, 1
• For nodules ≥1.5 cm: Perform ultrasound-guided fine-needle aspiration to exclude malignancy. 4, 1

This size threshold reflects the American College of Radiology's recommendation that balances the low malignancy risk against the need to avoid overdiagnosis of clinically insignificant papillary microcarcinomas. 4, 1

High-Risk Clinical Features That Lower the FNA Threshold

Even for nodules <1.5 cm, consider FNA when any of these high-risk factors are present: 1

• History of head and neck irradiation (increases malignancy risk approximately 7-fold) 1
• Family history of thyroid cancer, particularly medullary carcinoma or familial syndromes 1
• Age <15 years or male gender (higher baseline malignancy probability) 1
• Suspicious cervical lymphadenopathy on ultrasound examination 1
• Rapidly growing nodule (≥3 mm increase in any dimension) 5
• Firm, fixed nodule on palpation (suggests extrathyroidal extension) 1
• Vocal cord paralysis or compressive symptoms (dysphagia, dyspnea, voice changes) 1

Surveillance Protocol

For nodules not meeting FNA criteria, the surveillance strategy includes: 1

• Repeat ultrasound at 12–24 month intervals to assess for interval growth or development of suspicious features 1
• Monitor for compressive symptoms including dysphagia, dyspnea, or voice changes 1
• Document any growth ≥3 mm in any dimension, which warrants cytological evaluation regardless of initial TI-RADS category 5

Role of Molecular Testing and Thermal Ablation

• Molecular testing is generally not indicated for TI-RADS 3 nodules because the pretest probability of malignancy is so low (1.3–2.0%) that molecular markers add minimal clinical value. 1
• Thermal ablation is not indicated for TI-RADS 3 nodules unless they cause clinical symptoms (compression or cosmetic concerns) and are ≥2 cm in maximal diameter. 1

Diagnostic Performance and Clinical Validation

The negative predictive value of TI-RADS 3 classification is 94.6–100%, meaning that nodules without suspicious features are highly unlikely to harbor malignancy. 6 In surgical series, only 17% of resected TI-RADS 3 nodules proved malignant, compared to 65% for TI-RADS 4 and 84% for TI-RADS 5. 3

Critical Pitfalls to Avoid

• Do not perform FNA based solely on nodule size <1.5 cm without high-risk clinical features, as this leads to overdiagnosis of clinically insignificant papillary microcarcinomas that do not impact mortality or quality of life. 4, 1
• Do not rely on thyroid function tests (TSH, T3, T4) for malignancy assessment, as most thyroid cancers present with normal thyroid function. 5
• Do not override surveillance recommendations when nodules remain stable and lack high-risk features, even if patients express anxiety about cancer risk. 1
• Recognize that cytology has a 5–10% false-negative rate, so a benign FNA result should not supersede strong clinical suspicion when high-risk features develop during surveillance. 4