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Indications / TI-RADS Thresholds
Indications
- Sonographically suspicious thyroid nodule meeting ACR TI-RADS size thresholds (see table below)
- Nodule with microcalcifications, taller-than-wide shape, hypoechoic/very hypoechoic echogenicity, irregular margins, or extrathyroidal extension
- Diffuse rapid thyroid enlargement (rule out anaplastic carcinoma or lymphoma) — especially age >50
- Hashimoto thyroiditis with a discrete nodular focus (rule out lymphoma or PTC)
- Known primary malignancy with thyroid mass (evaluate for metastasis)
- High-risk history: prior head/neck radiation, family history thyroid cancer, MEN 2A/2B, Cowden syndrome
- Non-diagnostic prior FNA → repeat FNA or CNB
Contraindications
- SIR Category 1 (LOW bleeding risk) — routine coagulation testing not required for FNA
- INR >3.0 or platelets <20,000: consider correction before proceeding (especially if CNB planned)
- Purely cystic nodule (very low malignancy risk) — drainage ± cytology, not FNA
- Hot/hyperfunctioning nodule on scintigraphy — almost always benign, biopsy rarely indicated
- Uncooperative patient unable to hold still
ACR TI-RADS Biopsy Thresholds
| Category | Points | Risk | Follow-up Threshold | FNA Threshold |
|---|---|---|---|---|
| TR1 — Benign | 0 | Benign | No follow-up | No biopsy |
| TR2 — Not suspicious | 2 | <1% | No follow-up | No biopsy |
| TR3 — Mildly suspicious | 3 | ~5% | US if ≥1.5 cm | FNA if ≥2.5 cm |
| TR4 — Moderately suspicious | 4–6 | ~15% | US if ≥1 cm | FNA if ≥1.5 cm |
| TR5 — Highly suspicious | ≥7 | ~35% | US if ≥0.5 cm | FNA if ≥1 cm |
TI-RADS scoring: Composition (0–2), Echogenicity (0–3), Shape (0–3), Margin (0–3), Echogenic foci (0–3). Isthmus nodules carry higher malignancy risk — lower threshold for biopsy.
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Pre-Procedure Checklist
Review prior imaging. Confirm target nodule on dedicated thyroid US (not just CT scout). Note size, TI-RADS category, location (isthmus vs pole), and any associated lymphadenopathy. Plan biopsy approach and identify adjacent carotid/jugular.
Endocrine labs. Check TSH. If TSH <0.5 μU/mL (hyperthyroid), order I-123 scan before biopsy — hot nodules are almost always benign. Do not biopsy a hot nodule without scintigraphy first.
Anticoagulation. No specific hold required for FNA (SIR Cat 1). For CNB: treat as Cat 2 — INR <2.0, platelets >50,000. Hold warfarin 5 days for CNB if clinically appropriate.
Consent. Key risks: hematoma (most common), pain, non-diagnostic specimen (10–20%), false-negative (0–5%), infection (rare), tract seeding (extremely rare 0.00012% FNA), airway compromise from expanding hematoma (rare but emergent).
Target nodule selection. Biopsy no more than 2 nodules per session. In multinodular thyroid, prioritize the most sonographically suspicious nodule — not necessarily the largest.
Notify cytopathology. If ROSE (rapid on-site evaluation) is available, coordinate for specimen adequacy at the table. If not available, plan for 2–3 FNA needle passes per nodule.
NPO: Not required for FNA. Outpatient procedure. Patient should have a driver if sedation (rare) is planned.
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Relevant Anatomy
Key Structures
- Thyroid lobes: Butterfly-shaped gland straddling the trachea at C5–T1. Right and left lobes connected by the isthmus. Each lobe ~4–6 cm in length, 1.5–2 cm AP dimension.
- Isthmus: Overlies the 2nd–4th tracheal rings. Nodules here have a higher malignancy risk per cm than polar nodules.
- Carotid sheath: Lateral to each lobe — contains common carotid artery, internal jugular vein, vagus nerve. Identify with Doppler before every pass.
- Trachea: Posterior medial — don't confuse shadowing ring for a nodule.
- Parathyroids: Posterior to lobes; not typically at risk with careful anterior approach.
- Recurrent laryngeal nerve: Runs in the tracheoesophageal groove — no direct US visualization; stay anterior to paratracheal region.
Needle Approaches
- Lateral (parallel) approach: Needle enters skin lateral to thyroid, advances parallel to transducer axis into nodule. Full needle shaft visible — preferred by most operators. Reduces risk of tracheal or carotid injury.
- Anterior (perpendicular) approach: Short-axis — needle crosses transducer plane; tip seen as bright echogenic focus. Useful for small or isthmus nodules. Higher carotid risk if off-axis — use Doppler before every pass.
- Shoulder-roll positioning: Pillow under shoulders extends the neck, improving thyroid/isthmus access and creating separation between gland and trachea.
- Head rotation: Ipsilateral rotation 10–15° to the side of the biopsy increases access to posterior pole nodules.
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Technique
Default RadCall approach · share your own below
Supplies
High-freq linear US probe (15 MHz)
Hockey-stick probe (small parts)
Sterile probe cover + sterile gel
25g needle (FNA) ×3–4
5 mL syringe (aspiration technique)
18g or 20g CNB device (if CNB planned)
1% lidocaine
25g needle for local anesthesia
ChloraPrep / iodine prep
Sterile drape
Glass slides ×6+
95% ethanol fixative (Pap stain)
RPMI tube (cell block / flow)
Cold compress for post-procedure
Steps — FNA
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Position patient and survey
Supine, pillow under shoulders to extend neck. Turn head slightly away from target side. Perform full US survey with color Doppler. Identify target nodule, its largest diameter, solid vs. cystic components, and nearest vascular structures (carotid, jugular). Mark skin if helpful.
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Sterile prep and local anesthesia
ChloraPrep or iodine wipe. Sterile probe cover and gel. Infiltrate 1% lidocaine — skin wheal then deeper injection to thyroid capsule under US guidance (25g 1.5" needle). Anesthetize the capsule: pause needle at capsule and inject 0.5 mL lidocaine. Allow 60 seconds to dwell. Avoids major discomfort during FNA needle traversal of the capsule.
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Plan needle trajectory
Apply Doppler along planned path. Confirm no large vessel in tract. Lateral (parallel) approach preferred — aligns needle with US beam for full shaft visualization. Perpendicular (short-axis) for difficult isthmus nodules. Instruct patient: do not swallow or speak during needle insertion.
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FNA — Aspiration technique
25g needle attached to 5 mL syringe. Advance into nodule under real-time US. Create 1–2 mL negative pressure suction in syringe plunger. Move needle back and forth 30–60 times within nodule (short excursions). Rotate needle gently for shearing action. Release negative pressure before withdrawing — if plunger not released first, sample will be sucked into syringe and become unusable. Target solid/cellular component; avoid cystic areas.
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FNA — Non-aspiration (capillary) technique
25g needle without syringe. Advance into nodule and move back and forth ~30–60 times until material is visible in needle hub. No suction applied. Lower blood contamination — preferred for hypervascular nodules. If specimen appears adequate, blot hub onto slide. For very vascular nodules, start with non-aspiration, then switch to aspiration if yield is poor.
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Number of passes and specimen prep
Minimum 2–3 passes per nodule (up to 5 if no ROSE). If ROSE is available, pass 1–2 needles and check adequacy before additional passes. For partly cystic nodules: aspirate cystic component first (send for cytology, not discarded), then biopsy solid mural component. Prepare slide immediately: deposit on glass slide, smear with second slide, fix in 95% ethanol (Pap stain) or air-dry (Diff-Quik). Send remaining material in RPMI for cell block.
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CNB — when indicated
If FNA is non-diagnostic after adequate passes, or if lymphoma is suspected (flow cytometry requires intact architecture): use 18g or 20g CNB device coaxially or direct. Make superficial skin nick with 18g needle. Target nodule under real-time US. Confirm tip in nodule before firing. Obtain 2–3 cores. Short-throw device recommended given proximity of thyroid to carotid, trachea, and jugular — confirm throw stays within gland. Hold pressure 20–30 min post-CNB given higher bleeding risk vs FNA.
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Post-procedure hemostasis
Remove needle and apply firm manual pressure for minimum 5 minutes (FNA) or 20–30 minutes (CNB). Apply cold compress. US scan to assess for hematoma before discharge. If hematoma is visualized, continue pressure until stable.
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Troubleshooting
Problem
Needle tip not visible
Likely cause: Steep angle crossing the US beam (perpendicular approach); deep position; fine gauge needle.
Next step: Rock transducer gently while holding needle still — tip will appear as bright focus when beam intersects it. Partially withdraw and re-align so needle is more parallel to beam. Switch to lateral (parallel) approach. Try gentle in-out motion to create tip artifact.
Problem
Repeated non-diagnostic specimens
Likely cause: Blood dilution (too much suction or hypervascular nodule), operator technique, cystic component sampled instead of solid, inadequate passes.
Next step: Switch to non-aspiration (capillary) technique. Sample solid mural component only. Use ROSE if available. Ensure minimum 3 passes. If still non-diagnostic after adequate attempts, proceed to CNB. Consider opting for a larger gauge needle (21g spinal needle for difficult nodules).
Problem
Expanding hematoma during / after procedure
Likely cause: Vascular puncture, coagulopathy, or patient on anticoagulation. Large hematomas can compress airway — rare but emergent.
Next step: Apply firm direct pressure with US probe immediately. Hold for 3–5 minutes minimum. Monitor US for expansion. If hematoma expanding rapidly or patient develops swallowing difficulty/stridor — activate airway emergency, anesthesia to bedside, prepare for intubation. Most hematomas are minor and resolve with compression.
Problem
Nodule moves away from needle tip
Likely cause: Cervical lymph nodes and small thyroid nodules are mobile and can shift with needle pressure. Imprecise angle.
Next step: Use real-time US — watch tip approach nodule, adjust angle. Stabilize gland with non-needle hand if needed. For slippery lymph nodes, target the cortex not the center, and use a slightly more medial entry to "pin" the node against deeper structures.
Problem
Fluid-fluid level developing in cystic nodule
Likely cause: Hemorrhage into cystic component during biopsy — this is common and expected in part-cystic nodules.
Next step: Hold US probe pressure on overlying skin for 5 minutes. Monitor to ensure fluid level stops expanding. If stable — patient can be discharged normally. Document on post-procedure note. Pathology will confirm benign hemorrhagic change.
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Complications
Hemorrhagic
- Small intrathyroidal / subcapsular hematoma — most common; self-limited; compression and cold compress
- Perithyroidal hematoma — less common; observe; rarely requires intervention
- Large expanding hematoma with airway compression — rare but emergent. Pain + swelling + dysphagia + stridor. Requires immediate intubation and surgical decompression. Risk dramatically higher in anticoagulated patients.
Other
- Pain / discomfort — most common; ear-radiating pain from capsular irritation is expected and resolves
- Vasovagal reaction — manage with supine positioning, leg elevation; atropine if persistent bradycardia
- Non-diagnostic specimen — 10–20% of FNA procedures; repeat FNA or CNB. Male patients and taller-than-wide nodules are higher risk for non-diagnostic result.
- False negative — 0–5%; cytologic benign in malignant nodule. High-risk imaging features after benign FNA → repeat biopsy.
- Tract seeding — 0.00012% (FNA), 0.0011% (CNB). Extremely rare but documented.
- Infection — extremely rare. No antibiotic prophylaxis indicated.
- Recurrent laryngeal nerve palsy — rare; transient hoarseness possible; resolves spontaneously.
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Post-Procedure Care
Monitoring
- FNA: 20–30 min observation; post-procedure US to check for hematoma
- CNB: 20–30 min manual pressure + 30 min observation; post-procedure US
- Assess for neck swelling, dysphagia, hoarseness, or stridor before discharge
- Provide cold compress; instruct patient to apply intermittently for 2–4 hours
Discharge + Follow-up
- Outpatient discharge when asymptomatic and no expanding hematoma
- Return to ED for: rapidly enlarging neck swelling, difficulty swallowing/breathing, severe pain
- Bethesda result reported in 2–5 business days; notify ordering provider
- Bethesda I (non-diagnostic): Repeat FNA in 3 months or proceed to CNB
- Bethesda II (benign): Sonographic follow-up per TI-RADS (6 months if TR3–4; 12–24 months if TR2)
- Bethesda III–VI: Endocrine surgery / endocrinology referral
- Bethesda V–VI (malignant): Thyroidectomy ± lymph node dissection; radioactive I-131 for papillary/follicular types
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Critical Pearls
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Check TSH before any thyroid biopsy: If TSH <0.5 (hyperthyroid), order I-123 scan first. Hot nodules are benign — do not biopsy without ruling out hot nodule first.
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Lateral (parallel) approach is the default: Full shaft visibility reduces risk of overshooting into carotid/trachea. Perpendicular is useful for isthmus but requires meticulous tip tracking.
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Anesthetize the thyroid capsule: The capsule is where most pain occurs. Pause at the capsule, inject 0.5 mL lidocaine, and wait 60 seconds before advancing. This small step dramatically improves patient comfort for multi-pass procedures.
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Non-aspiration first for vascular nodules: High vascularity leads to blood-diluted specimens with aspiration technique. Start with capillary (non-aspiration) — only switch to aspiration if yield is inadequate.
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Release suction before withdrawing the needle: If the plunger is still pulled back when you withdraw, the specimen is sucked into the syringe barrel and becomes non-diagnostic. Always release suction first.
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ROSE saves passes: If on-site cytopathology is available, request rapid adequacy — adequacy is confirmed in 1–2 passes vs. needing 3–5 without it. Reduces bleeding and patient discomfort.
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For part-cystic nodules: Aspirate cyst first (send fluid; don't discard), then biopsy the solid mural component. The solid component is where malignant cells are.
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Biopsy no more than 2 nodules per session: Biopsying multiple nodules increases cost, risk, and time with minimal added benefit. Prioritize the most suspicious nodule by US features, not by size alone.
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Suspect lymphoma → CNB required: FNA cytology cannot subtype lymphoma — flow cytometry and immunophenotyping from CNB cores are required. Submit in saline, not formalin.
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Benign FNA with high-risk features → don't stop: If imaging is highly suspicious (microcalcifications, extrathyroidal extension, associated cervical LAD) and FNA returns benign, this is a high-risk benign — discuss with endocrine surgery. In one series, all thyroid nodules with associated cervical LAD were malignant.
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Specimen Handling
FNA Cytology
- Papanicolaou (wet fix): Smear on glass slide → immediately fix in 95% ethanol. Best for nuclear chromatin detail — identifying ground-glass nuclei and nuclear grooves of papillary carcinoma.
- Diff-Quik / Giemsa (air dry): Smear and air-dry. Better for cytoplasm and colloid visualization. Allow to air-dry completely before staining.
- Cell block (RPMI or saline): Rinse syringe into RPMI tube after slide prep. Used for IHC, molecular markers, flow cytometry.
- ThinPrep: If institutional protocol — deposits material in preservative solution for liquid-based cytology. Requires specific technique and experience.
CNB Histology + Special
- Routine histology: 10% formalin for IHC, architectural analysis, molecular markers
- Suspected lymphoma: Fresh saline (NOT formalin) — flow cytometry requires viable cells; formalin will kill them
- Molecular / NGS: RPMI or snap-freeze for BRAF, RAS, RET/PTC, PAX8-PPARγ testing on indeterminate nodules
- Cyst fluid: Centrifuge and submit as cytologic specimen; don't discard — malignant cells may be present
Bethesda System Reference
| Bethesda Category | Malignancy Risk | Recommended Management |
|---|---|---|
| I — Non-diagnostic | 1–4% | Repeat FNA in 3 months (or CNB) |
| II — Benign | 0–3% | Sonographic follow-up per TI-RADS |
| III — AUS / FLUS | 10–30% | Repeat FNA, molecular testing, or surgery |
| IV — Follicular neoplasm | 25–40% | Molecular testing or lobectomy |
| V — Suspicious malignancy | 50–75% | Surgery (lobectomy or thyroidectomy) |
| VI — Malignant | 97–99% | Thyroidectomy ± LN dissection ± RAI |
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References & Resources
Primary sources · Key data · Related procedures
Key Guidelines
- ATA Management Guidelines for Thyroid Nodules 2015
- AACE/ACE/AME Thyroid Nodule Guidelines
- SIR Standards of Practice for Thyroid Biopsy
Primary References
- Haugen BR et al. (ATA Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer). Thyroid. 2016;26(1):1-133.
- Gharib H et al. (AACE/AME Task Force on Thyroid Nodules). American Association of Clinical Endocrinologists, Associazione Medici Endocrinologi, and European Thyroid Association medical guidelines for clinical practice for the diagnosis and management of thyroid nodules. J Endocrinol Invest. 2010;33(5 Suppl):1-50.
- Cibas ES, Ali SZ. The 2017 Bethesda System for Reporting Thyroid Cytopathology. Thyroid. 2017;27(11):1341-1346.