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Table 3 Sonographic Patterns, Estimated Risk of Malignancy, and Fine-Needle Aspiration Guidance for Thyroid Nodules, reproduced from 2015 American Thyroid Association guidelines [14]

From: Indolent thyroid cancer: knowns and unknowns

Sonographic pattern US features Estimated risk of malignancy, % FNA size cutoff (largest dimension)
High suspicion Solid hypoechoic nodule or solid hypoechoic component of a partially cystic nodule with one or more of the following features: irregular margins (infiltrative, microlobulated), microcalcifications, taller than wide shape, rim calcifications with small extrusive soft tissue component, evidence of ETE >70–90 Recommend FNA at ≥1 cm
Intermediate suspicion Hypoechoic solid nodule with smooth margins without microcalcifications, ETE, or taller than wide shape 10–20 Recommend FNA at ≥1 cm
Low suspicion Isoechoic or hyperechoic solid nodule, or partially cystic nodule with eccentric solid areas, without microcalcification, irregular margin or ETE, or taller than wide shape. 5–10 Recommend FNA at ≥1.5 cm
Very low suspicion Spongiform or partially cystic nodules without any of the sonographic features described in low, intermediate, or high suspicion patterns. <3 Consider FNA at ≥2 cm Observation without FNA is also a reasonable option
Benign Purely cystic nodules (no solid component) <1 No biopsy