This is the official guideline endorsed by the specialty associations involved in the care of head and neck cancer patients in the UK. This paper provides recommendations on the management of thyroid cancer in adults and is based on the 2014 British Thyroid Association guidelines. Recommendations • Ultrasound scanning (USS) of the nodule or goitre is a crucial investigation in guiding the need for fine needle aspiration cytology (FNAC). (R) • FNAC should be considered for all nodules with suspicious ultrasound features (U3-U5). If a nodule is smaller than 10 mm in diameter, USS guided FNAC is not recommended unless clinically suspicious lymph nodes on USS are also present. (R) • Cytological analysis and categorisation should be reported according to the current British Thyroid Association Guidance. (R) • Ultrasound scanning assessment of cervical nodes should be done in FNAC-proven cancer. (R) • Magnetic resonance imaging (MRI) or computed tomography (CT) should be done in suspected cases of retrosternal extension, fixed tumours (local invasion with or without vocal cord paralysis) or when haemoptysis is reported. When CT with contrast is used pre-operatively, there should be a two-month delay between the use of iodinated contrast media and subsequent radioactive iodine (I131) therapy. (R) • Fluoro-deoxy-glucose positron emission tomography imaging is not recommended for routine evaluation. (G) • In patients with thyroid cancer, assessment of extrathyroidal extension and lymph node disease in the central and lateral neck compartments should be undertaken pre-operatively by USS and cross-sectional imaging (CT or MRI) if indicated. (R) • For patients with Thy 3f or Thy 4 FNAC a diagnostic hemithyroidectomy is recommended. (R) • Total thyroidectomy is recommended for patients with tumours greater than 4 cm in diameter or tumours of any size in association with any of the following characteristics: multifocal disease, bilateral disease, extrathyroidal spread (pT3 and pT4a), familial disease and those with clinically or radiologically involved nodes and/or distant metastases. (R) • Subtotal thyroidectomy should not be used in the management of thyroid cancer. (G) • Central compartment neck dissection is not routinely recommended for patients with papillary thyroid cancer without clinical or radiological evidence of lymph node involvement, provided they meet all of the following criteria: classical type papillary thyroid cancer, patient less than 45 years old, unifocal tumour, less than 4 cm, no extrathyroidal extension on ultrasound. (R) • Patients with metastases in the lateral compartment should undergo therapeutic lateral and central compartment neck dissection. (R) • Patients with follicular cancer with greater than 4 cm tumours should be treated with total thyroidectomy. (R) • I131 ablation should be carried out only in centres with appropriate facilities. (R) • Serum thyroglobulin (Tg) should be checked in all post-operative patients with differentiated thyroid cancer (DTC), but not sooner than six weeks after surgery. (R) • Patients who have undergone total or near total thyroidectomy should be started on levothyroxine 2 µg per kg or liothyronine 20 mcg tds after surgery. (R) • The majority of patients with a tumour more than 1 cm in diameter, who have undergone total or near-total thyroidectomy, should have I131 ablation. (R) • A post-ablation scan should be performed 3-10 days after I131 ablation. (R) • Post-therapy dynamic risk stratification at 9-12 months is used to guide further management. (G) • Potentially resectable recurrent or persistent disease should be managed with surgery whenever possible. (R) • Distant metastases and sites not amenable to surgery which are iodine avid should be treated with I131 therapy. (R) • Long-term follow-up for patients with differentiated thyroid cancer (DTC) is recommended. (G) • Follow-up should be based on clinical examination, serum Tg and thyroid-stimulating hormone assessments. (R) • Patients with suspected medullary thyroid cancer (MTC) should be investigated with calcitonin and carcino-embryonic antigen levels (CEA), 24 hour catecholamine and nor metanephrine urine estimation (or plasma free nor metanephrine estimation), serum calcium and parathyroid hormone. (R) • Relevant imaging studies are advisable to guide the extent of surgery. (R) • RET (Proto-oncogene tyrosine-protein kinase receptor) proto-oncogene analysis should be performed after surgery. (R) • All patients with known or suspected MTC should have serum calcitonin and biochemical screening for phaeochromocytoma pre-operatively. (R) • All patients with proven MTC greater than 5 mm should undergo total thyroidectomy and central compartment neck dissection. (R) • Patients with MTC with lateral nodal involvement should undergo selective neck dissection (IIa-Vb). (R) • Patients with MTC with central node metastases should undergo ipsilateral prophylactic lateral node dissection. (R) • Prophylactic thyroidectomy should be offered to RET-positive family members. (R) • All patients with proven MTC should have genetic screening. (R) • Radiotherapy may be useful in controlling local symptoms in patients with inoperable disease. (R) • Chemotherapy with tyrosine kinase inhibitors may help in controlling local symptoms. (R) • For individuals with anaplastic thyroid carcinoma, initial assessment should focus on identifying the small proportion of patients with localised disease and good performance status, which may benefit from surgical resection and other adjuvant therapies. (G) • The surgical intent should be gross tumour resection and not merely an attempt at debulking. (G).