Thyroid Nodule: Monitoring or Surgery? TIRADS, FNA Biopsy and Surgical Indications

Thyroid nodules are extremely common in adults — about 50-60% of people screened by ultrasound have at least one nodule. Frequency increases with age; over 60 it can reach 70%. Important: presence of a nodule does not mean cancer. 90-95% of nodules are benign.

Most thyroid nodules are detected incidentally on imaging done for another reason (neck ultrasound, CT, MRI, carotid Doppler). These "incidental" nodules are usually low-risk. Clinically the more important nodules are palpable or symptomatic ones.

Thyroid cancer is annually rare (10-15 cases per 100,000), but diagnosis has risen with increased imaging in the last 30 years. Most thyroid cancers progress slowly and have excellent treatment outcomes — especially the papillary type. Related service: our thyroid surgery programme.

TIRADS (Thyroid Imaging Reporting and Data System) is a system standardising malignancy risk of thyroid nodules by ultrasound features. ACR-TIRADS (American) and EU-TIRADS (European) versions are widely used. Each nodule is assigned a TIRADS category 1-5.

Assessment criteria: composition (cystic, solid, mixed), echogenicity (anechoic, hypoechoic, isoechoic, hyperechoic), shape (oval vs vertical), margin (smooth, irregular, lobulated), echogenic foci (calcifications). Each feature is scored; the total determines the TIRADS category.

TIRADS 1-2: benign or very low risk (<1%) — no biopsy, yearly follow-up. TIRADS 3: low risk (1-5%) — biopsy if over 2.5 cm. TIRADS 4: intermediate risk (5-20%) — biopsy if over 1.5 cm. TIRADS 5: high risk (>20%) — biopsy if over 1 cm (sometimes smaller).

FNAB is the gold standard for histopathological diagnosis of a thyroid nodule. No local anaesthesia needed; under ultrasound guidance a thin needle samples cells from the nodule. The procedure takes 10-15 minutes and the patient returns to normal activity immediately afterwards.

Results are reported using the Bethesda System: I (insufficient sample — repeat), II (benign, ~97%), III (atypia of undetermined significance, AUS/FLUS, 10-30% cancer risk), IV (suspicious for follicular neoplasm, 25-40%), V (suspicious for malignancy, 60-75%), VI (malignant, ~97%).

Bethesda III and IV ("indeterminate") are the hardest categories — biopsy is not conclusive. Molecular tests (Afirma, ThyroSeq) or repeat FNAB may help. Alternatively, diagnostic hemithyroidectomy (lobectomy with pathology review) may be recommended.

Two core thyroid operations exist: hemithyroidectomy (only one lobe + isthmus removed) and total thyroidectomy (both lobes entirely). The decision is not single-answer; nodule location, size, pathology and patient preference all play a role.

Hemithyroidectomy is preferred for: unilateral 1-4 cm nodules, Bethesda III-IV (diagnostic), low-risk papillary carcinoma (<1 cm, no capsule invasion, no lymph node metastasis), benign nodules (symptomatic 4 cm+). Advantage: lower risk of hypoparathyroidism and recurrent laryngeal nerve injury; most patients do not need thyroid hormone supplementation.

Total thyroidectomy is needed for: bilateral nodules, Bethesda V-VI (malignant), aggressive types (medullary, anaplastic), invasive papillary carcinoma (capsule invasion, nodal metastasis, > 4 cm), Graves disease, symptomatic multinodular goitre. Advantage: cancer recurrence surveillance (thyroglobulin) and radioactive iodine therapy possible. More detail: thyroid nodule page.

Two classic complications of thyroid surgery: recurrent laryngeal nerve (RLN — moves the vocal cord) injury, and hypoparathyroidism (parathyroid gland injury). In experienced hands both rates are around 1-3%; with low-volume surgeons they rise to 5-10%.

Transient RLN injury (2-5%) usually resolves in 3-6 months — presents as hoarseness. Permanent RLN injury (0.5-1%) causes lasting hoarseness. Intraoperative neuromonitoring (IONM) reduces this risk. Bilateral RLN injury is very rare but life-threatening — may need tracheostomy.

Transient hypoparathyroidism (10-25%) after total thyroidectomy resolves with calcium-vitamin D support. Permanent hypoparathyroidism (1-3%) requires lifelong calcium. Tetany, muscle cramps and paraesthesia are symptoms.

Other complications: haematoma (1%, emergent drainage), wound infection (<1%), seroma (2-3%, mostly self-resolving). Scar quality depends on the surgeon's incision technique — a proper horizontal Kocher incision usually fades within 6-12 months.

For low-risk nodules not requiring surgery, the follow-up protocol depends on TIRADS class and size. A reasonable approach: ultrasound every 6 months in the first year, then yearly. For stable nodules after 2-3 years the interval may extend to 1.5-2 years.

In case of significant growth (both dimensions ≥20% or volume ≥50%) or worsening ultrasound features, biopsy is repeated. Rapid growth (clear increase in 3-6 months) raises malignancy suspicion and warrants aggressive evaluation.

Thyroid function tests (TSH, fT4) are checked yearly. If TSH is suppressed (suggesting a toxic nodule), scintigraphy is performed — hot (autonomous) nodules have very low cancer risk but may require treatment for hyperthyroidism.

Patient education during follow-up matters: the presence of a nodule is not an emergency, the cancer probability is low, yearly checks may suffice. Anxiety may push some patients toward unnecessary surgery — the surgeon should discuss in detail and share realistic probabilities.

After hemithyroidectomy, about 70-80% of patients do not need thyroid hormone — the remaining lobe produces enough. In 20-30%, subclinical or overt hypothyroidism develops and levothyroxine is started. TSH is checked at 6-8 weeks and then yearly.

After total thyroidectomy every patient needs levothyroxine — starting dose is weight-based (1.6 mcg/kg/day). TSH target depends on malignancy risk: 0.5-2 mIU/L for low risk; 0.1-0.5 mIU/L for moderate-high risk. Lifelong, taken every morning on empty stomach.

If cancer is diagnosed, follow-up additionally includes thyroglobulin, neck ultrasound (every 6 months for the first 2 years, then yearly) and radioactive iodine scan if needed. In low-risk papillary microcarcinoma recurrence is 1-2%; long-term survival 98-99%.

Quality of life: most patients return to normal life within 1-2 weeks after surgery. The scar fades over 6-12 months. With properly dosed thyroid hormone replacement, fatigue, weight changes and metabolic complaints are usually absent. Related reading: our Istanbul thyroid surgery page.