Solitary Thyroid Nodule

Definition and significance: a discrete lesion within the thyroid, radiologically distinct from surrounding parenchyma. About 95% are benign, but every nodule deserves evaluation because a few harbour malignancy.

Epidemiology: palpable in 3–7% of adults, but present in around 50% on ultrasound or autopsy. Frequency and goitre size increase with age, and nodular goitre is commoner in women and in iodine-deficient areas. In the Pescopagano (iodine-deficient) survey, goitre prevalence rose from 30% in young adults to 75% in those aged 55–65.

Key principle: the risk of malignancy is the same for a solitary nodule and for a nodule within a multinodular goitre.

Red flags requiring urgent referral: rapid growth over a few weeks, stridor, hoarseness (recurrent laryngeal nerve), cervical lymphadenopathy, fixation, prior neck irradiation.

First-line investigation: serum TSH plus high-resolution ultrasound. Ultrasound is not a population screening test, but any palpable nodule must be scanned.

If TSH is low or suppressed → radioisotope scan. A “hot” (autonomous) nodule is virtually never malignant and is managed as hyperthyroidism — 131I is the treatment of choice in old age, especially with cardiovascular disease. A “cold” nodule requires FNAC.

If TSH is normal or high → risk-stratify by ultrasound using EU-TIRADS: category 2 (pure cyst / spongiform) ≈0%; category 3 (ovoid, smooth, iso/hyperechoic) 2–4%; category 4 (mildly hypoechoic) 6–17%; category 5 (irregular shape or margins, microcalcification, marked hypoechogenicity) 26–87%.

FNAC is the cornerstone of diagnosis, and accuracy improves with ultrasound guidance. Perform for nodules ≥10 mm with irregular margins, chaotic intranodular vascularity, taller-than-wide shape, or microcalcification; for nodules <10 mm only if clinical or ultrasound features are suspicious. No ultrasound finding alone is diagnostic.

Limitation of FNAC: inadequate or indeterminate results in 10–25%; surgery is then usually advised for diagnosis, although most such nodules prove benign.

Follow-up and treatment: benign nodule → ultrasound at 12 months, then at 2–5 year intervals. Repeat FNA only for >50% volume growth, ≥20% increase in two dimensions, new suspicious features, or new symptoms. Routine TSH-suppressive levothyroxine is NOT recommended — harm outweighs benefit and it can cause exogenous thyrotoxicosis with cardiac and bone consequences. Malignant or suspicious → surgery; large compressive non-toxic goitre → surgery or radioiodine. Supporting datum: in a prospective Italian multicentre study of 992 patients (1567 benign nodules) followed 5 years, only 11.1% grew, thyroid cancer was found in 0.3%, and age ≥60 was associated with a lower risk of nodule growth. Latest Updates & Current Practice (2023–Present) — 3 Points ETA 2023 thyroid nodule guideline: minimally invasive techniques are now first-line for symptomatic benign nodules — ethanol ablation for cystic/predominantly cystic lesions, and thermal ablation (radiofrequency, microwave, laser, HIFU) for solid nodules, giving 57–77% volume reduction sustained at 5 years without general anaesthesia. The ATA issued a 2023 statement on safe performance and training for these techniques. ATA 2025 guidelines now separate differentiated thyroid cancer from nodule management: lobectomy is preferred over total thyroidectomy for unilateral cT1N0M0 tumours ≤2 cm; active surveillance and percutaneous ablation are formally accepted alternatives for papillary microcarcinoma; molecular diagnostics have an expanded role in Bethesda III/IV nodules; and TSH suppression has been simplified to a binary target (“within” versus “below” the normal range). Relevance to the older patient: these de-escalated pathways (surveillance, lobectomy, ablation) are particularly suited to frail elderly patients, in whom the competing risks of thyroidectomy, hypocalcaemia and lifelong levothyroxine often outweigh the risk from an indolent tumour.