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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