What is 'Thyroid Cancer'? It is a cancer the affects the thyroid organ in the neck. There are four main types of Thyroid Cancer: Papillary, Follicular, Anaplastic and Medullary. If this is not the cancer type you're looking for, please explore the information about other types of Head and Neck Cancers.
Cancer occurs when cells become abnormal, grow uncontrollably and have the potential to spread to other parts of the body. These cells build up to form a mass (or lump).
This is the most common type of thyroid cancer (about 75% of all cases). It tends to grow very slowly, but often spread to lymph nodes. It can be cured or controlled in most people and is rarely fatal
This accounts for about 5-10% cases. It grows slowly and tends to stay in the thyroid, however it can spread to the lungs or bones if diagnosed late. If diagnosed early, most people with follicular Thyroid Cancer can be treated successfully.
This type of thyroid cancer is rare (less than 1%) but is very aggressive and can be challenging to treat.
This is different to other thyroid cancers because they develop in cells called ‘C cells’ that do not produce thyroid hormone and can be due to having an underlying genetic predisposition. All patients who develop this type of thyroid cancer should be assessed to decide if they need genetic testing.
There is also Poorly Differentiated Thyroid Cancer, which makes up to 5% of Thyroid Cancer and usually occurs in older people. It can frequently be non iodine-avid.
The thyroid gland lies at the base of the neck. It is shaped like a butterfly and wraps around the windpipe (trachea) beneath the voice box (larynx). The parts of the thyroid are:
wings of the butterfly (left and right lobes)
body of the butterfly (isthmus, joining the left and right lobes)
there is a small part that lies over the voice-box (pyramidal lobe).
When the thyroid is larger than normal it is called a goitre. Lumps in the thyroid are called nodules. Most thyroid nodules are benign but some can be cancerous. Here is a 3D video explainer that explains the thyroid and Thyroid Cancer further:
Glands that release hormones into the blood stream are called endocrine glands, the thyroid is the largest endocrine gland of the body.
There are two types of thyroid hormone, tri-iodothyronine (T3) and thyroxine (T4). These hormones control the speed at which the cells work (metabolism), and are important in brain development and growth in children. These hormones also determine how sensitive other organs are to endocrine hormones. Thyroid hormone is made in cells called follicular cells. The amount of thyroid hormone in the blood stream is controlled by the pituitary gland. The pituitary gland, is a small endocrine gland that sits under the brain. It releases a hormone into the blood called thyroid stimulating hormone (TSH). When doctors order thyroid tests, they will look at all three of these hormones (T3, T4 and TSH) but TSH is the most important.
Diagram of the thyroid and surrounding areas:
Doctors often can’t explain why a person gets cancer. But we do know what makes some cancers more likely. The two main causes of Thyroid Cancer are:
Being female — In Australia women are about four times more likely than men to get Thyroid Cancer
Age — while Thyroid Cancer can occur at any age, it is most common in people aged 40–60 years.
Having a diet low in iodine also increases risk of Thyroid Cancer, but this is rare in Australia as iodine is added to salt and other foods. Other factors that increase the risk of Thyroid Cancer include:
Radiation — this is a very important risk factor for Thyroid Cancer, either because of medical treatment (particularly low dose radiation treatment in childhood), or from environmental exposure such as atomic explosions or nuclear fallout
Having a non-cancerous (benign) thyroid disease — like an enlarged thyroid (goitre), thyroid nodules (adenomas) or inflammation of the thyroid (thyroiditis), or having one of these conditions in your family
A family history of Thyroid Cancer or an inherited gene change (mutation) in the RET oncogene (a protein coding gene)
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