What is the recommended evaluation and management of a thyroid nodule in a patient from Kerala, and why is the risk of thyroid cancer higher in this region?

Thyroid Nodule Management in Kerala: Evaluation and Cancer Risk

In Kerala, thyroid nodules should be evaluated using the standard international approach with ultrasound and EU-TIRADS scoring, followed by fine-needle aspiration biopsy (FNAB) for nodules ≥10mm with EU-TIRADS 5, ≥15mm with EU-TIRADS 4, or ≥20mm with EU-TIRADS 3 features, and the rising thyroid cancer incidence in Kerala appears to be driven by true disease increase rather than overdiagnosis. 1, 2

Initial Evaluation Approach

Start with TSH measurement as the first laboratory test 3:

• If TSH is low (<0.4 mIU/L): Perform thyroid scintigraphy first, as functioning "hot" nodules are almost never malignant and do not require FNAB 4, 3
• If TSH is 0.4-1.0 mIU/L: Consider scintigraphy only if FNAB is already indicated based on ultrasound 4
• If TSH ≥1.0 mIU/L: Proceed directly to ultrasound evaluation without scintigraphy 4

Ultrasound Risk Stratification (EU-TIRADS)

All patients with palpable nodules or clinical risk factors require ultrasound examination 3. The ultrasound should assess:

• Shape: Taller-than-wide configuration increases malignancy risk
• Margins: Irregular borders suggest cancer
• Echogenicity: Hypoechoic nodules are more suspicious
• Calcifications: Microcalcifications are highly concerning for papillary cancer
• Composition: Solid nodules carry higher risk than cystic

FNAB Indications Based on Size and Risk

Perform ultrasound-guided FNAB for 1, 5:

• EU-TIRADS 5 nodules ≥10mm (malignancy risk 26-87%)
• EU-TIRADS 4 nodules ≥15mm (malignancy risk 6-17%)
• EU-TIRADS 3 nodules ≥20mm (malignancy risk 2-4%)

Do NOT biopsy nodules <5mm regardless of appearance 3. For nodules 5-10mm, only perform FNAB if EU-TIRADS 5 features are present with suspicious lymph nodes or extrathyroidal extension 3.

Critical technical point: FNAB must be ultrasound-guided using 23-27G needles 6. The needle should target the solid portion of mixed nodules and avoid passing through ultrasound gel 6.

Follow-Up Protocol for Benign Nodules

For nodules with benign cytology (Bethesda II) or no FNAB indication 1:

• First follow-up: 1-2 years after initial evaluation
• Subsequent follow-up: Every 2-4 years if stable
• Exception: EU-TIRADS 5 nodules with benign FNAB require annual monitoring for 5 years 1

Monitoring can be discontinued in elderly patients with long-standing, non-suspicious nodules 1.

Why Kerala Has Higher Thyroid Cancer Rates

The doubling of thyroid cancer incidence in Kerala from 2010-2020 represents true disease increase, not overdiagnosis 2. This conclusion is based on critical evidence:

• Papillary thyroid microcarcinoma (PTMC) proportion remained stable at 18.9%, only marginally increasing from 14.7% to 17.9% over the decade 2
• In regions with overdiagnosis (like many Western countries), PTMC rates rise disproportionately to >50% of all thyroid cancers 7
• 64% of Kerala's microcarcinomas occurred in patients <45 years, suggesting clinically relevant disease rather than incidental findings 2

The study from Kerala's government medical colleges is particularly important because these facilities serve populations with less healthcare-seeking behavior and reduced access to imaging, making overdiagnosis less likely 2. This contrasts sharply with high-income settings where increased imaging drives artificial incidence increases 7.

Common Pitfalls to Avoid

Do not perform levothyroxine suppression therapy in euthyroid patients with benign nodules—this practice is obsolete and not recommended 3.

Do not repeat ultrasound too frequently. Most nodules remain stable, and the risk of initially undetected cancer is only 1-3% 1. Excessive monitoring leads to patient anxiety and healthcare costs without improving outcomes.

For non-diagnostic FNAB (Bethesda I): Repeat the biopsy after 1-3 months 1. If the second attempt is also non-diagnostic, consider core-needle biopsy or close surveillance rather than immediate surgery 1.

In mixed (partially cystic) nodules: Ensure FNAB targets the solid component, which should be assessed separately using EU-TIRADS criteria 5. The solid portion must be ≥10mm and accessible for biopsy 5.