Thyroid Cancer

Thyroid cancer is a cancer that starts in the thyroid — a small, butterfly-shaped gland at the front of the neck that makes hormones controlling how the body uses energy. It is relatively uncommon and is more frequently diagnosed in women.

There are several types. Papillary and follicular thyroid cancers (together called differentiated thyroid cancer) are the most common, usually grow slowly, and have a very good outlook. Medullary and anaplastic thyroid cancers are rarer; anaplastic is aggressive but uncommon.

No. Lumps and nodules in the thyroid are common and the great majority are not cancer. However, because a lump can occasionally be a sign of thyroid cancer, any new or changing neck lump should be checked so the cause can be found.

The most common symptom is a painless lump or swelling in the neck, low down at the front. It may gradually get bigger. Some people notice a persistently hoarse voice, difficulty swallowing or breathing, or swollen glands in the neck.

Many thyroid cancers cause no symptoms early on and are found by chance during a scan or examination for another reason. Thyroid cancer does not usually change hormone levels, so most people do not feel unwell from it.

The exact cause is often unknown. Recognized risk factors include exposure of the neck to radiation, particularly in childhood, a family history of thyroid cancer or certain inherited conditions, and some benign thyroid conditions.

It is more common in women than men and can occur at any age. Having a risk factor does not mean cancer will develop, and most people with thyroid cancer have no clear cause.

Assessment usually starts with an examination of the neck and an ultrasound scan, which shows the size and features of a lump. Blood tests check how the thyroid is working. The key test is a fine-needle aspiration, where a thin needle takes a small sample of cells from the lump to look for cancer.

If cancer is confirmed, further scans may be done to check whether it has spread. Because thyroid nodules are common and mostly benign, these tests help tell the small number that are cancer from the many that are not.

The main treatment is surgery to remove part or all of the thyroid gland (thyroidectomy), sometimes along with nearby lymph nodes if the cancer has spread there. The plan is agreed by a specialist team based on the type and extent of the cancer.

After surgery for differentiated (papillary or follicular) thyroid cancer, radioactive iodine (I-131) treatment is often used. The thyroid naturally absorbs iodine, so radioactive iodine is taken up by any remaining thyroid or cancer cells and destroys them while sparing the rest of the body. Thyroid hormone replacement (levothyroxine) is taken for life, serving both to replace missing hormones and to suppress TSH, which helps prevent cancer recurrence. Rarer or advanced types may need other treatments such as targeted therapy or radiotherapy.

The outlook for the common types of thyroid cancer is excellent, and most people are successfully treated, including many whose cancer has spread to nearby lymph nodes. Papillary and follicular cancers in particular have very high long-term survival.

After treatment, regular follow-up with blood tests and scans checks that the cancer has not come back and that thyroid hormone replacement is at the right level. There is no proven way to prevent thyroid cancer, so seeing a doctor promptly about a neck lump is the most useful step.