Thyroid Nodule Biopsy / FNA

Background and indications

Ultrasound-guided thyroid fine needle aspiration (FNA) is the reference examination for characterizing thyroid nodules and determining their benign or malignant nature. Thyroid nodules are very common (30-50% of the adult population), but only 5-10% are malignant.

FNA is indicated based on size and ultrasound criteria (EU-TIRADS or ACR-TIRADS classification): nodules > 10 mm with suspicious features, nodules > 15-20 mm with intermediate features, and any nodule with associated suspicious lymphadenopathy. Core needle biopsy may be performed as complement for non-diagnostic or indeterminate cytology.

Pre-procedure assessment

Assessment includes recent thyroid ultrasound with EU-TIRADS classification of all nodules, thyroid panel (TSH, free T4), and verification of adjusted anticoagulant therapy. Coagulation panel is not routinely required for fine needle aspiration.

Procedure

Without anesthesia (25-27G fine needle) or under local anesthesia (18-20G core needle biopsy), the needle is inserted into the nodule under real-time ultrasound guidance. For FNA, 2-4 passes are performed with syringe aspiration. Material is spread on slides and/or placed in liquid medium. For core biopsy, 2-3 micro-cores are obtained. The procedure takes 10 to 20 minutes.

Results and scientific evidence

Ultrasound-guided thyroid FNA offers 83-97% sensitivity and 92-98% specificity for thyroid cancer diagnosis. Results are classified according to the Bethesda system (I to VI). Non-diagnostic cytology rate is 5-15%. Adding molecular biology (genomic profiling) on indeterminate cytology (Bethesda III-IV) improves diagnostic performance.

Risks and complications

Complications are very rare: mild local pain (10-20%), cervical hematoma (< 1%, generally minor and self-resolving), vasovagal reaction (< 1%). FNA is considered one of the safest percutaneous procedures in interventional radiology.

Recovery

Immediate return to activities. A dressing is applied for 1-2 hours. Cytology results are available within 5-10 days. For indeterminate cytology, core biopsy or close monitoring may be offered.

Practical information

The procedure is performed on an outpatient basis. It is performed by an interventional radiologist or an endocrinologist trained in ultrasound.