Table 1.

Categorization of nodules based on the degree of suspicious features and the likelihood of malignancy

NODULE FEATURESTHRESHOLD SIZE FOR FNALIKELIHOOD OF MALIGNANCY
High suspicion≥ 1.0 cm> 70%–90%
Solid hypoechoic nodule or solid hypoechoic component of partially cystic nodule with ≥ 1 of the following features:
  • Irregular margins (infiltrative, microlobulated)

  • Microcalcification

  • Taller-than-wide shape

  • Rim calcification with small extrusive soft tissue component

  • Evidence of extrathyroidal extension

Intermediate suspicion≥ 1.0 cm10%–20%
Hypoechoic solid nodule with smooth margin without the following:
  • Microcalcifications

  • Extrathyroidal extension

  • Taller-than-wide shape

Low suspicion≥ 1.5 cm5%–10%
Isoechoic or hyperechoic solid nodule, or partially cystic nodule with eccentric solid area without any ultrasonographic features
Very low suspicion≥ 2.0 cm< 3%
Spongiform or partially cystic without any ultrasonographic features
Purely cystic nodulesNo biopsy required< 1%
  • FNA—fine-needle aspiration.