How should I approach the investigation of a thyroid nodule found incidentally on imaging?

When approaching the investigation of an incidentally discovered thyroid nodule on imaging, the initial steps in General Practice involve assessing for urgent features and arranging blood tests to guide referral pathways ¹.

• Initial Assessment and Blood Tests:
  • Arrange serum thyroid function tests (TFTs) in primary care, as these results can help guide the appropriate referral pathway ¹. TFTs are strongly recommended during the initial assessment of a suspected thyroid nodule ¹.
  • Do not routinely arrange further investigations such as a neck ultrasound scan in primary care, as this may cause diagnostic delay ¹.
• Referral Pathways:
  • Arrange an urgent referral (for an appointment within 2 weeks) to a thyroid surgeon or endocrinologist if there is:
    • An unexplained thyroid lump ¹.
    • A thyroid mass associated with unexplained hoarseness or voice change ¹.
    • A thyroid mass associated with cervical lymphadenopathy or supraclavicular lymphadenopathy ¹.
    • Sudden onset of a rapidly expanding painless thyroid mass, significantly increasing in size over days and weeks ¹.
    • A suspected thyroid nodule with other red flags or risk factors for malignancy ¹.
    • A suspected thyroid nodule with associated compressive symptoms, such as breathlessness or dysphagia ¹.
    • For a child with a thyroid nodule or goitre, arrange an urgent referral to a general paediatrician or paediatric endocrinologist ¹.
  • Arrange a routine endocrinology referral if there is:
    • A non-suspicious thyroid nodule or nodular goitre with abnormal TFT results (the risk of thyroid malignancy is low) ¹.
    • A non-suspicious thyroid nodule with normal TFT results ¹.
    • Sudden-onset painful expansion in a pre-existing thyroid lump (likely due to haemorrhage into a benign thyroid cyst) ¹.
    • An incidental thyroid nodule picked up on an ultrasound scan, CT, or MRI, which is more than 1 cm in diameter, if there are no suspicious features of malignancy ¹.
  • Consider monitoring in primary care with no need for specialist referral, depending on clinical judgement, if there is:
    • An adult with a history of a longstanding unchanging thyroid nodule or mass over several years, with no palpable cervical lymphadenopathy and no other red flags or risk factors for malignancy ¹.
    • A non-palpable, asymptomatic thyroid nodule picked up incidentally on an ultrasound scan, CT, or MRI, which is less than 1 cm in diameter, with no associated lymphadenopathy and no other red flags or risk factors for malignancy ¹.

  Further Investigations (Typically in Secondary Care):

  • If malignancy is suspected, ultrasound is offered to image palpable thyroid enlargement or focal nodularity ³. Ultrasound of incidental findings on imaging may be considered if clinical factors suggest malignancy ³.
  • Greyscale ultrasound with an established system for grading ultrasound appearance should be offered as the initial diagnostic test when investigating thyroid nodules for malignancy ²,³. Ultrasound reports should specify the grading system used, include information on features like echogenicity, microcalcifications, border, shape, internal vascularity, and lymphadenopathy, provide an overall assessment of malignancy, confirm both lobes were assessed, and document cervical lymph node assessment ³.
  • Fine needle aspiration cytology (FNAC) is offered to people who meet the threshold using an established system for grading ultrasound appearance ². Ultrasound guidance should be used when performing FNAC ³.
  • Management and further sampling options are determined by the initial FNAC results, which are reported using the Royal College of Pathologists modification of the British Thyroid Association (BTA) reporting system ². For example, an inadequate (Thy1) result typically leads to repeat sampling, while benign (Thy2) results may lead to discharge or repeat ultrasound/FNAC if concerns persist ².
  • Radioisotope scans are not routinely used for the initial diagnosis of thyroid cancer ². Calcitonin testing is not used to assess thyroid nodules unless medullary thyroid cancer is suspected ².