What are ATA guidelines on the diagnosis of differentiated thyroid cancers?

Updated: Jun 24, 2020
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Answer

ATA guidelines state that FNAB provides the most economical and accurate methodology for diagnosing differentiated thyroid cancers. Due to potential false negatives or sampling error, it is recommended that FNAB procedures be performed under ultrasound (US) guidance. US guidance is particularly important for nodules located posteriorly and for those that are difficult to palpate. Additionally, certain features found on US examination are predictive for malignancy and may guide FNAB decision-making. [1]  

Papillary thyroid cancer is characterized by the following US features:

  • Solid or predominantly solid
  • Hypo-echoic
  • Microcalcifications (highly specific)
  • Infiltrative irregular margins (common)
  • Increased nodular vascularity

Follicular thyroid cancer is characterized by the following US features:

  • Iso- to hyper-echoic
  • Thick irregular halo

Benign US features are as follows:

  • Purely cystic nodule
  • Spongiform appearance (aggregation of multiple micro-cystic components >50% volume)

In 2017, an ATA task force recommended that encapsulated follicular variant papillary thyroid carcinoma (eFVPTC) without capsular or vascular invasion be reclassified as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), given its excellent prognosis. This was a weak recommendation based on moderate-quality evidence. [9]


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