Assessment of thyroid lesions (general)

Assessment of thyroid lesions is commonly encountered in radiological practice.

Thyroid mass breakdown
Risk factors of a nodule being malignant
  • young
  • male
  • solitary
  • cold on thyroid scan
  • past history of radiotherapy

The first three risk factors are really a reflection that elderly women with multiple benign thyroid nodules are very common.

Radiographic features

Ultrasound
  • taller-than-wide in axial/transverse dimension, microcalcifications, local invasiveness, microlobulated contour, and hypoechogenicity are suspicious features
  • size criteria are controversial and continously evolving
  • cervical lymphadenopathy is a feature
  • for detailed assessment, see: assessment of thyroid lesions (ultrasound)
Nuclear medicine

A single 'cold' nodule has a 10% chance of being malignant. A single 'hot' nodule has <1% chance of being malignant.

Treatment and prognosis

Indications for FNA

The criteria developed by the American Thyroid Association (2015) 11 are often used in clinical practice. See: ATA guidelines for assessment of thyroid nodules.

Indications for FNA according to Society of Radiologists in Ultrasound (2008) 4

  • nodule ≥1.0 cm at the largest diameter if microcalcifications are present
  • nodule ≥1.5 cm if the nodule is solid or if there are coarse calcifications within the nodule

Additional recommendations for FNA by the American Association of Clinical Endocrinologists 4:

  • FNA recommended for nodules <`10 mm whenever clinical information or ultrasound features raises suspicion about the presence of a malignancy

 

Management of FNA results
  • benign: clinical and imaging follow up
  • follicular neoplasm
  • atypia of uncertain significance / follicular lesion of uncertain significance (AUS/FLUS)
    • 3-6%
    • repeat FNA
      • two samples obtained at second biopsy
      • if AUS/FLUS again (~20%) on the first sample, then the risk of malignancy is 5-15% 10
      • the second sample may be sent for gene sequencing, if available (gene expression classifier)
        • if benign, then normal clinical and imaging follow up
        • if suspicious, 50% risk of malignancy
  • malignant: partial or total thyroidectomy with lymph node exploration
Staging

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