Thyroid Cancer
Types, symptoms, what your FNAC result means, and when surgery is recommended — explained for patients.
What is Thyroid Cancer?
Thyroid cancer is a malignant tumour of the thyroid gland — the butterfly-shaped gland at the front of the neck that regulates metabolism. It is one of the most treatable cancers when detected early, with five-year survival rates exceeding 95% for the most common type.
Most thyroid cancers present as a thyroid nodule — a lump in the thyroid gland. The vast majority of thyroid nodules (95%+) are benign. However, a small proportion are malignant and require surgery.
Types of Thyroid Cancer
Papillary (85%)
Most common. Excellent prognosis. Spreads to lymph nodes but rarely fatal. Treated with surgery ± radioactive iodine.
Follicular (10%)
Second most common. Spreads via bloodstream. Surgery and radioactive iodine. Good prognosis in most cases.
Medullary (3–4%)
Arises from C-cells. Does not respond to radioactive iodine. Associated with MEN2 syndromes. Genetic testing important.
Anaplastic (<2%)
Rare and aggressive. Requires urgent specialist assessment. Combined surgery, radiation, and systemic therapy.
Symptoms
Most thyroid cancers cause no symptoms at all and are discovered incidentally on ultrasound or during examination for an unrelated condition. When symptoms do occur they include a lump or swelling in the neck, difficulty swallowing or breathing if the tumour is large, hoarseness if the recurrent laryngeal nerve is involved, and enlarged lymph nodes in the neck.
Understanding Your FNAC Result — Bethesda Classification
Fine needle aspiration cytology (FNAC) is a simple needle biopsy performed under ultrasound guidance. Results are reported using the Bethesda system:
| Category | Description | Cancer Risk | Next Step |
|---|---|---|---|
| I | Non-diagnostic | Uncertain | Repeat FNAC |
| II | Benign | 0–3% | Surveillance — no surgery |
| III | AUS / FLUS | ~15% | Repeat or molecular testing |
| IV | Follicular neoplasm | 25–40% | Hemithyroidectomy |
| V | Suspicious for malignancy | 60–75% | Total thyroidectomy |
| VI | Malignant | >97% | Total thyroidectomy + neck dissection |
A Bethesda II result means benign — the nodule has less than 3% chance of being cancerous. Surveillance with repeat ultrasound is all that is required in most cases.
Treatment
Surgery is the main treatment for thyroid cancer. Total thyroidectomy (complete removal of the thyroid gland) is standard for most thyroid cancers. Hemithyroidectomy (removal of one lobe) is used for low-risk cancers or for diagnostic purposes when FNAC is inconclusive.
After total thyroidectomy, daily thyroxine tablets are required for life — a simple replacement for the hormone the thyroid no longer produces. Most patients adapt quickly and live entirely normally.
Radioactive iodine is given after surgery for papillary and follicular cancers when indicated — it destroys any remaining thyroid tissue and reduces recurrence risk.
For detailed information about thyroid surgery, visit drnarayana.in/thyroid-surgery
Dr. Narayana Subramaniam
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