Is a thyroid nodule that has increased by 1.7 cm in one dimension and 1.4 cm in another dimension concerning?

Yes, an increase of 1.7 cm and 1.4 cm in thyroid nodule dimensions is highly concerning and warrants immediate fine-needle aspiration biopsy.

Any thyroid nodule demonstrating growth of ≥3 mm (0.3 cm) in any dimension during surveillance is considered significant progression and requires cytological evaluation, making your nodule's growth of 17 mm and 14 mm extremely alarming. 1

Why This Degree of Growth Demands Immediate Action

• Growth of this magnitude far exceeds the threshold for significant progression. Active surveillance studies from Japan define nodule enlargement as an increase of ≥3 mm compared to baseline, and your nodule has grown approximately 5-6 times beyond this threshold 1

• Substantial growth is one of the strongest predictors of malignancy in thyroid nodules. While the baseline malignancy risk for thyroid nodules is approximately 5-15%, rapidly growing nodules carry significantly elevated risk and represent a high-risk clinical feature that mandates tissue diagnosis 1, 2

• The measurement variability argument does not apply here. While studies of pulmonary nodules show that changes <1.7 mm may represent measurement error, your nodule's growth of 14-17 mm is an order of magnitude larger and represents unequivocal true progression 1

Immediate Diagnostic Algorithm

Step 1: Perform ultrasound-guided fine-needle aspiration (FNA) within 1-2 weeks

• Target the solid portions of the nodule if it has mixed cystic-solid components 3
• Document all suspicious ultrasound features including hypoechogenicity, microcalcifications, irregular margins, absence of peripheral halo, and central hypervascularity 1, 3
• Measure serum calcitonin to screen for medullary thyroid cancer, which has higher sensitivity than FNA alone 3, 4
• Obtain TSH level, as higher TSH is associated with increased differentiated thyroid cancer risk 4

Step 2: Assess for high-risk clinical features that modify management

• History of head and neck irradiation (increases malignancy risk 7-fold) 3, 4
• Family history of thyroid cancer, particularly medullary carcinoma or familial syndromes 3, 4
• Age <40 years (younger patients show higher progression rates in active surveillance studies) 1
• Presence of suspicious cervical lymphadenopathy on ultrasound 3, 4
• Compressive symptoms including dysphagia, dyspnea, or voice changes 3

Step 3: Management based on FNA results (Bethesda classification)

• Bethesda II (Benign): Even with benign cytology, a nodule demonstrating this degree of growth requires repeat FNA in 3-6 months, as false-negative rates occur in 11-33% of cases, particularly with larger nodules 3

• Bethesda III-IV (Indeterminate): Proceed directly to molecular testing (BRAF, RAS, RET/PTC, PAX8/PPARγ) to refine malignancy risk, as 97% of mutation-positive nodules are malignant 3, 4

• Bethesda V-VI (Suspicious or Malignant): Immediate referral to endocrine surgeon for total or near-total thyroidectomy with pre-operative assessment of cervical lymph node compartments 3, 4

Critical Context About Nodule Size and Growth

• Larger nodules (>2 cm) actually have lower malignancy rates than smaller nodules when evaluated at a single time point (approximately 15-20% vs. 30% for nodules <2 cm), but this statistical observation becomes irrelevant when a nodule demonstrates significant growth 5, 6

• Growth itself is an independent risk factor that supersedes baseline size considerations. Active surveillance studies show that only 8% of papillary microcarcinomas enlarge by ≥3 mm over 10 years, making your nodule's dramatic growth highly atypical for benign disease 1

• The risk of follicular carcinoma increases with nodule size, rising from 6% in nodules 1.0-1.9 cm to 16% in nodules >4 cm, and follicular carcinoma cannot be distinguished from follicular adenoma on cytology alone, requiring surgical excision for definitive diagnosis 6, 3

Common Pitfalls to Avoid

• Do not delay FNA based on "normal" thyroid function tests. Most thyroid cancers present with normal TSH, T3, and T4 levels 4

• Do not accept a single benign FNA result as definitive in the setting of dramatic growth. False-negative rates are highest (6-8%) in nodules 3-6 cm, often due to encapsulated follicular variant of papillary carcinoma 5

• Do not order radionuclide scanning in euthyroid patients, as it does not add value for malignancy risk assessment; ultrasound features and growth pattern should guide management 3

• Do not rely solely on ultrasound features to exclude malignancy. While certain features (microcalcifications, irregular margins, marked hypoechogenicity) increase specificity, their absence does not rule out cancer, especially in a growing nodule 1, 3