a. Presentations of papillary thyroid carcinoma

1. Solitary thyroid nodule or goitre
   • Usually a slow-growing, painless thyroid swelling.
   • Patient is commonly euthyroid.
2. Cervical lymph-node metastasis
   • May present as a lateral neck mass, sometimes more obvious than the primary thyroid lesion.
   • Cervical nodal disease is common because papillary carcinoma spreads predominantly by lymphatics.
3. Incidental lesion
   • Small papillary microcarcinoma may be non-palpable and detected incidentally on ultrasound, CT, surgery for another thyroid condition, or histology.
4. Features of local invasion in advanced disease
   • Hoarseness or change of voice due to recurrent laryngeal nerve involvement.
   • Dysphagia, dyspnoea, stridor, fixed thyroid mass, or pain referred to the ear.
5. Rare distant metastases
   • Usually lung, less often bone, presenting with respiratory symptoms or bone pain/pathological fracture.

b. Investigations

1. Clinical assessment
   • History: duration and growth of swelling, prior neck irradiation, family history, dysphagia, dyspnoea, hoarseness.
   • Examination of thyroid, central and lateral cervical lymph nodes, and signs of fixation or retrosternal extension.
2. Thyroid function tests
   • Serum TSH and free T4, though most patients are euthyroid.
   • A suppressed TSH may prompt radionuclide scanning to identify a hyperfunctioning nodule.
3. High-resolution ultrasound of thyroid and neck
   • Defines size, site, multifocality, extrathyroidal extension, and suspicious central/lateral lymph nodes.
   • Guides fine-needle aspiration.
4. Ultrasound-guided FNAC
   • FNAC of the thyroid nodule confirms cytological diagnosis.
   • Aspirate suspicious cervical nodes as well. Thyroglobulin estimation in lymph-node needle washout can support metastatic differentiated thyroid cancer.
5. Assessment for extent of disease
   • Flexible laryngoscopy to document vocal-cord mobility, especially with hoarseness, large tumour, posterior lesion, or suspected invasion.
   • Contrast CT or MRI of neck and upper mediastinum if bulky nodal disease, retrosternal extension, or local invasion is suspected.
   • Chest CT and other imaging, such as bone scan or PET-CT, only if there is clinical or biochemical suspicion of distant metastasis.

Treatment of papillary thyroid carcinoma

• Thyroid lobectomy (hemithyroidectomy) for a low-risk, intrathyroidal, unifocal tumour confined to one lobe, with no clinical nodal disease or distant metastasis.
• Total thyroidectomy is preferred for:
  • Larger tumour, especially >4 cm
  • Bilateral or multifocal disease
  • Gross extrathyroidal extension
  • Clinically involved cervical nodes
  • Distant metastasis
  • When postoperative radioactive iodine treatment or thyroglobulin surveillance is planned.

• Perform therapeutic central compartment (level VI) dissection when central nodes are clinically/radiologically involved.
• Perform selective lateral neck dissection for biopsy-proven metastatic lateral cervical nodes.
• Do not perform routine prophylactic lateral neck dissection.
• Routine prophylactic central neck dissection in clinically node-negative small PTC is controversial and is not routinely required.

• High-risk tumours
• Gross extrathyroidal extension
• Large-volume nodal metastases
• Distant metastases
• Persistent or recurrent iodine-avid disease.

• Give lifelong levothyroxine after total thyroidectomy.
• It replaces thyroid hormone and suppresses TSH, reducing stimulation of any residual differentiated thyroid cancer.
• Degree of TSH suppression is tailored to recurrence risk and response to treatment. Avoid excessive suppression in low-risk patients, especially older women, because of atrial fibrillation and osteoporosis risk.

• Clinical examination and neck ultrasound.
• Serum thyroglobulin with anti-thyroglobulin antibodies, especially after total thyroidectomy.
• Diagnostic radioiodine scan or cross-sectional imaging when recurrence or metastasis is suspected.

• Resectable locoregional recurrence: reoperation.
• Iodine-avid metastases: radioactive iodine.
• External-beam radiotherapy: selected unresectable local disease or palliation.
• Progressive radioactive iodine-refractory disease: molecular testing and targeted systemic therapy, such as a multikinase inhibitor or mutation-directed treatment.