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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
Nuclear medicine

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

Indications for FNA

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

  • nodule 1.0 cm or more at the largest diameter if microcalcifications are present
  • nodule 1.5 cm or larger 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 smaller than 10 mm whenever clinical information or ultrasound features raises suspicion about the presence of a malignancy

Size criteria for indication for FNA according American thyroid association (2009) 6:

  • high risk history 
    • with suspicious sonographic features: >5 mm
    • without suspicious sonographic features: >5 mm
    • with abnormal cervical lymph nodes: all; FNA may be obtained from the lymph node as well
    • with microcalcifications: ≥1 cm
  • solid nodule
    • hypoechoeic: >1 cm
    • solid nodule, iso or hyperechoeic: ≥1-1.5 cm
  • mixed cystic-solid nodule 
    • with suspicious sonographic features: ≥1.5-2 cm
    • without suspicious sonographic features: ≥2 cm
  • spongiform nodule: ≥2 cm
  • purely cystic: FNA not indicated

High risk factors:

  • history of childhood head and neck irradiation
  • family history of thyroid cancer or a thyroid cancer syndrome
  • prior hemithyroidectomy with discovery of thyroid cancer
  • increased activity on PET scan
  • presence of MEN-2 associated oncogene

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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