In most people cancer of the thyroid develops very slowly. The first sign is usually a painless lump in the neck which gradually gets bigger. Occasionally, a thyroid tumour may press on the gullet (oesophagus) or windpipe (trachea) and cause difficulty in swallowing or breathing.

Very rarely, the first symptoms may be caused by secondary tumours in the bones or lungs after the cancer has spread beyond the thyroid.

It is unusual for cancer of the thyroid to affect the production of thyroid hormones, so symptoms of an over- or under-active thyroid are rare.

If you notice a lump in your neck, or any of the above symptoms, you should see your doctor as soon as possible. However, most thyroid swellings (or goitres) are benign (non-cancerous).