What is the follow-up for a thyroid ultrasound showing mild thyromegaly with a 7mm nodule on the right and a 1cm nodule on the left?

Management of Thyroid Nodules: 7mm TR4 and 1cm TR3

The 1cm TR3 nodule on the left should undergo ultrasound-guided fine-needle aspiration biopsy (FNA) now, while the 7mm TR4 nodule on the right should be followed with repeat ultrasound at 3-4 month intervals for the first year. 1, 2

Immediate Management of the 1cm TR3 Nodule

Fine-needle aspiration cytology (FNAC) should be performed on any thyroid nodule >1 cm, making the 1cm left-sided nodule an appropriate candidate for immediate biopsy. 1, 3

Rationale for FNA at 1cm Threshold

• The established guideline threshold is 1cm for nodules without high-risk features, and this nodule meets that size criterion 1, 3
• Even TR3 (low-to-intermediate suspicion) nodules warrant FNA at 1cm size, as thyroid cancer occurs in approximately 5% of all thyroid nodules 1
• FNA remains the most accurate and cost-effective method for preoperative diagnosis of thyroid malignancy 2, 3

Technical Considerations for FNA

• Ultrasound guidance should be used to ensure accurate sampling 2
• If the initial FNA yields inadequate samples, the procedure should be repeated under ultrasound guidance 1, 4
• Measurement of serum calcitonin should be considered as part of the diagnostic workup to screen for medullary thyroid cancer, which has higher sensitivity than FNA alone 1, 3

Surveillance Strategy for the 7mm TR4 Nodule

Nodules smaller than 1cm should be followed with ultrasound at 3-4 month intervals rather than immediate biopsy, even when classified as TR4. 1, 2

Follow-Up Protocol

• Repeat ultrasound should be performed at ≤4-month intervals in the first year 1
• If there is no increase in size or development of additional suspicious features over 12 months (three controls after four months), surveillance can be shifted back to regular six-month intervals 1
• The nodule should be re-evaluated for FNA if it grows to ≥1cm or develops additional high-risk features during surveillance 1, 2

Exceptions That Would Lower the FNA Threshold

Consider FNA even for nodules <1cm if any of these high-risk clinical features are present: 1, 2

• History of head and neck irradiation 1, 2
• Positive family history of thyroid cancer 1, 2
• Presence of suspicious cervical lymphadenopathy 1, 2
• Multiple suspicious ultrasonographic features (hypoechogenicity, microcalcifications, irregular or microlobulated margins, absence of peripheral halo) 1, 4

Critical Pitfalls to Avoid

Do Not Rely on Thyroid Function Tests

• Thyroid function tests (TSH, T3, T4) are of little help in diagnosing thyroid cancer, as most thyroid cancers present with normal thyroid function 1, 2
• The decision to perform FNA should be based on nodule size and ultrasound characteristics, not thyroid function 3

Management of Indeterminate FNA Results

• If FNA shows follicular neoplasia with normal TSH and "cold" appearance on thyroid scan, surgery should be considered 1, 3
• For repeatedly nondiagnostic results on FNA, the presence of two or more suspicious ultrasound findings (particularly irregular or microlobulated margins and microcalcifications) should prompt surgical referral rather than continued surveillance 4, 5
• Imaging-cytology discordance (benign cytology but suspicious ultrasound features) carries a malignancy rate of 23.3% and warrants repeat FNA 5

Avoid Overdiagnosis

• Do not perform FNA on nodules <1cm without high-risk features, as this leads to overdiagnosis and overtreatment of clinically insignificant cancers 2
• Most thyroid carcinomas detected nowadays are micropapillary thyroid carcinomas (<1cm) carrying an excellent long-term prognosis 1

Documentation and Monitoring

• Document all ultrasound features systematically, including echogenicity, margins, calcifications, and vascularity patterns 6, 7
• Maintain a surveillance schedule with clear documentation of nodule measurements over time 1
• Consider molecular testing (BRAF, RAS, RET/PTC, PAX8/PPARγ) only for indeterminate cytology results, as 97% of mutation-positive nodules are malignant 2