Table 1.
An overview of the standardized thyroid nodule US scoring systems proposed or endorsed by international practice guidelines.
| Risk score | AACE/AME/ACE | ATA | EU-TIRADS | K-TIRADS |
|---|---|---|---|---|
| Suspicious US features |
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| Category |
Low-risk:
Cysts (fluid component >80%) Mostly cystic nodules with reverberating artifacts and not associated with suspicious US signs Isoechoic spongiform nodules, either confluent or with regular halo. Risk of malignancy: 1% FNA >20 mm (selective)a |
Benign: Purely cystic nodules (no solid component) Risk of malignancy: <1% FNA is not indicated |
Benign (EU-TIRADS 2):
Pure/anechoic cysts; entirely spongiform nodules Risk of malignancy: ≈ 0% FNA is not indicated |
Benign:
Spongiform Partially cystic nodule with comet-tail artifact Pure cyst Risk of malignancy: <1–3 FNA ≥20 mm |
|
Very low suspicion:
Spongiform or partially cystic nodules without any of the US features defining low-, intermediate,- or high-suspicion patterns Risk of malignancy: <3% FNA ≥20 mm or observation |
Low-Risk (EU-TIRADS 3):
Oval shape, smooth margins, isoechoic, or hyperechoic, without any feature of high risk Risk of malignancy: 2–4% FNA >20 mm |
Low suspicion: Partially cystic or isohyperechoic nodule without any of 3 suspicious US features* Risk of malignancy: 3–15% FNA ≥15 mm |
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Low suspicion:
Isoechoic or hyperechoic solid nodule, or partially cystic nodule with eccentric solid area without: microcalcifications, irregular margin, extrathyroidal extension, taller than wide shape Risk of malignancy: 5–10% FNA ≥15 mm |
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Intermediate-risk:
Slightly hypoechoic (vs. thyroid tissue) or isoechoic nodules, with ovoid-to-round shape, smooth or ill-defined margins May be present: Intranodular vascularization Elevated stiffness at elastography, Macro or continuous rim calcifications Indeterminate hyperechoic spots Risk of malignancy: 5–15% FNA: >20 mm |
Intermediate suspicion:
Hypoechoic solid nodule with smooth margins without: microcalcifications, extrathyroidal extension or taller than wide shape Risk of malignancy: 10–20% FNA ≥10 mm |
Intermediate-Risk (EU-TIRADS 4):
Oval shape, smooth margins, mildly hypoechoic, without any feature of high risk Risk of malignancy: 6–17% FNA >15 mm |
Intermediate suspicion:
Solid hypoechoic nodule without any suspicious US feature or partially cystic or isohyperechoic nodule with any of the following: microcalcification, non-parallel orientation (taller-than-wide), spiculated/microlobulated margin Risk of malignancy: 15–50% FNA ≥10 mm |
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High-risk:
Nodules with ≥1 of the following: Marked hypoechogenicity (vs. prethyroid muscles) Spiculated or lobulated margins Microcalcifications Taller-than-wide shape (AP>TR) Extrathyroidal growth Pathologic adenopathy Risk of malignancy: 50–90%b FNA ≥10 mm (5 mm, selective)c |
High suspicion:
Solid hypoechoic nodule or solid hypoechoic component of partially cystic nodule with ≥1 of the following: Irregular margins (infiltrative, microlobulated) Microcalcifications Taller than wide shape Rim calcifications with small extrusive soft tissue Extrathyroidal extension Risk of malignancy: >70–90% FNA ≥10 mm |
High-Risk (EU-TIRADS 5):
Nodules with ≥1 of the following: Non-oval shape Irregular margins Microcalcifications Marked hypoechogenicity Risk of malignancy: 26–87% FNA >10 mm |
High suspicion:
Solid hypoechoic nodule with any of the following: Microcalcification Nonparallel orientation (taller-than-wide) Spiculated/microlobulated margin Risk of malignancy: >60 FNA ≥10 mm (>5 mm selective) |
Growing nodule, high-risk history, before surgery, or local therapies.
In accordance with the presence of 1 or more suspicious findings.
FNA is recommended for the following nodules: Subcapsular or paratracheal lesions; Suspicious lymph nodes or extrathyroid spread; Positive personal or family history of thyroid cancer: History of head and neck irradiation, coexistent suspicious clinical findings (e.g., dysphonia).