Thyroid cancer

Thyroid nodules

A thyroid nodule is a discrete lesion (palpable and/or on ultrasound) distinct from the rest of the gland. Nodules are common and the great majority are benign.

Causes: dominant nodule in a multinodular goitre (most likely), colloid cyst, or a true solitary nodule (adenoma or carcinoma — papillary/follicular).

Work-up (per the AJGP nodule guidance):

1. TSH first — a suppressed TSH suggests an autonomously functioning (“hot”) nodule, which is rarely malignant and warrants a radionuclide uptake scan.
2. Ultrasound to characterise the nodule and assess sonographic risk features (microcalcification, irregular margins, taller-than-wide shape, marked hypoechogenicity, suspicious nodes).
3. Fine-needle aspiration cytology — the investigation of choice — guided by nodule size and sonographic risk.

Thyroid carcinoma

Presentations: a painless nodule, a hard nodule in an enlarged gland, or lymphadenopathy. Papillary carcinoma is the most common and, although rare relative to benign disease, is important not to miss given its high cure rate.

FNA is the investigation of choice. Treatment often involves total thyroidectomy, ablative radioiodine, and levothyroxine (for replacement and TSH suppression). Post-treatment surveillance uses thyroglobulin as a tumour marker (should be undetectable).