ATA guidelines for assessment of thyroid nodules

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The American Thyroid Association (ATA) guidelines for assessment of thyroid nodules are meant to improve inter- and intra-reader consistency during assessment of thyroid nodules on ultrasound, and to facilitate communication with referring endocrinologists.

The 2015 guidelines stress the importance of the sonographic pattern of the nodule for risk stratification. This, as well as the size of the nodule, are the two main criteria for FNA.

Initial evaluation

  • serum thyrotropin (TSH) should be obtained
    • if the TSH is below normal limits, thyroid scintigraphy should be pursued
  • an incidental finding of focal FDG uptake in a >1 cm thyroid nodule is concerning and FNA is warranted
    • if <1 cm the nodule may be monitored similarly to a subcentimeter thyroid nodule with a high risk sonographic pattern
    • if the thyroid demonstrates diffuse uptake compatible with chronic lymphocytic thyroiditis, further imaging or FNA is not warranted

Sonographic pattern

On a thyroid ultrasound, a nodule is classified into one of five categories:

  • benign pattern (0% risk): no biopsy
  • very low suspicion pattern (<3% risk): biopsy if ≥2 cm (or ultrasound observation)
  • low suspicion pattern (5-10% risk): biopsy if ≥1.5 cm
  • intermediate suspicion pattern (10-20% risk): biopsy if ≥1 cm
  • high suspicion pattern (>70-90% risk): biopsy if ≥1 cm
Benign pattern (0% risk)
  • completely cystic nodules with well-defined walls
Very low suspicion pattern (<3% risk)
  • spongiform nodules and nodules with interspersed cystic spaces, without any of the features in more suspicious patterns
Low suspicion pattern (5-10% risk)
  • isoechoic or hyperechoic nodule
  • partially cystic nodule with a peripheral solid component
  • none of the following features:
    • microcalcifications (see other points below)
    • irregular margins
    • extrathyroidal extension
    • taller than wide
Intermediate suspicion pattern (10-20% risk)
  • hypoechoic solid nodule with smooth margins
  • none of the following features:
    • microcalcifications (see other points below)
    • irregular margins
    • extrathyroidal extension
    • taller than wide
High suspicion pattern (>70-90% risk)
  • solid hypoechoic nodule (or solid hypoechoic component of a partially cystic nodule), with at least one of these features:
    • microcalcifications (see other points below)
    • irregular margins (infiltrative, microlobulated)
    • extrathyroidal extension
    • taller than wide
    • rim calcifications with an extrusive soft tissue component
    • lymphadenopathy

Other points

  • dystrophic calcifications other than microcalcifications (e.g. coarse macrocalcification, rim calcifications) increase risk, but to a lesser degree than microcalcifications
  • a survey of cervical lymph nodes should be performed in all neck ultrasound studies

See also