Thyroid cancer is an uncommon type of cancer that begins in the thyroid gland.
What is the thyroid gland?
The thyroid gland is at the base of the throat, just below the Adam’s apple. It's made up of two sections (lobes) that are located on either side of the windpipe.
The thyroid gland’s main role is to release hormones, which are powerful messenger chemicals that have an important effect on the functions of the body. These hormones include:
- thyroxine and triiodothyronine (also known as T4 and T3 respectively), and
- calcitonin.
Thyroxine and triiodothyronine help regulate the speed of your body’s functions (metabolic rate). Your metabolic rate influences many different bodily functions, from how fast your heart beats to how fast you can burn up calories.
Calcitonin helps control the levels of calcium in your blood. Calcium is a mineral that has many important functions, such as building strong bones and preventing blood clots. Calcitonin is not essential for health, and people who have had their entire thyroid gland removed suffer no after-effects from lacking calcitonin.
How common is thyroid cancer?
Thyroid cancer is one of the rarer types of cancer, accounting for only 1% of all cancer cases.
Women are more likely to get thyroid cancer than men (about 75% of all cases).
In recent years the reported number of new cases of thyroid cancer has been slowly rising. This may be the result of improvements in technology making it easier to detect the condition at an earlier stage, rather than thyroid cancer becoming more widespread.
Risk factors for thyroid cancer include exposure to radiation, particularly during childhood.
Common types of thyroid cancer
Health professionals classify thyroid cancer according to the types of cells in the thyroid gland that are affected. The two most common types of thyroid cancer are:
- Papillary thyroid cancer (an estimated 80% of all thyroid cancer).
- Follicular thyroid cancer (an estimated 11% of all thyroid cancer).
These two types of thyroid cancer develop and are treated in the same way and are usually grouped together under the term differentiated thyroid cancers (DTC).
Rarer types of thyroid cancer
Rarer types of thyroid cancer include:
- Medullary cancer (about 4% of all thyroid cancer).
- Anaplastic cancer (between 1 and 2% of all thyroid cancer).
- Thyroid lymphoma (between 1 and 2% of all thyroid cancer).
These rarer types of thyroid cancer are usually more aggressive, with a greater chance of spreading to another part of the body (metastasis).
Prognosis
The prognosis for DTCs is usually good. These types of thyroid cancer are slow-growing and are usually confined to the thyroid gland when they are diagnosed. DTCs can usually be cured using a combination of surgery to remove some or all of the thyroid gland and radioactive iodine treatment.
The prognosis for non-DTC types of thyroid cancer is less favourable. If a complete cure is not possible, treatment can help to control symptoms and delay the spread of the cancer for many years.