Thyroid Nodules and Cancers

Thyroid nodules are often picked up as incidental findings on clinical examination, or on imaging (usually carotid ultrasound) for another purpose. They can cause problems if they become large and compress the oesophagus / trachea.

Causes of clinically detectable thyroid nodule:

• Dominant nodule in an otherwise impalpable multinodular goitre.
• Simple colloid nodule
• Benign thyroid cyst
• Adenomas
• Malignancy

History

• Symptoms of hyper or hypothyroidism.
• Family history of thyroid cancer or MEN syndromes.
• Previous radiation to the neck.

Workup

• TSH is the first-line investigation.
  • Reduced TSH warrants
    • a radionuclide scan to determine if the nodule is
      •  hot (increased uptake – suggestive of toxic adenoma) or 
      • cold (reduced uptake). 
  • Hot nodules are almost never malignant: manage as per toxic adenoma. 
  • Normal or low TSH mandates an ultrasound scan of the nodule. 
  • If there are any suspicious features on the ultrasound, then FNA should be performed. 
  • Most radiology reports will suggest whether or not the nodule should be biopsied. 
• Beware of a cold nodule in Graves disease
  • the TSH is low and there is generalised increase of tracer uptake on the radionuclide scan, but the nodule itself is still cold –> warrants USS +/- FNA.
• CT scan may be warranted if there are compressive symptoms.

Treatment and Followup

• Hot nodule: refer to endocrinologist / surgeon for RAI +/- surgery (occasionally CBZ/PTU)
• Non-benign nodule on FNA: refer to endocrine surgeon
• Benign cold nodule: 
  • If hypothyroid, replace with thyroxine. In iodine-endemic areas, add iodine supplements.
  • Nodules that are not biopsied (doesn’t fulfil criteria), or are benign on FNA, should have serial USS after 6-18 months. If there is an increase of 20% in the size, the FNA should be repeated. 
• Any nodules causing symptoms (eg compression) should be referred.

FNA Results

FNA results are reported using the Bethesda system:

Essentially, an inadequate result requires repeat FNA (or send to endocrine surgeon so they can do it); benign can be followed up as above; and atypical or malignant requires specialist referral.

Thyroid Cancer

4 subtypes:

• Papillary: 75-85% of cases; excellent prognosis (20 year survival >99% if early)
• Follicular: 10-20% of cases; 5 year survival > 90%
• Medullary: 5-10% of cases; 5 year survival >80%
• Anaplastic: rare; 5 year survival 7%

The goals of treatment are:

• Thyroidectomy
• RAI to treat any mets
• Lifelong thyroxine therapy