Thyroid cancer is a rare type of cancer that affects the thyroid gland, a small gland at the base of the neck.
The most common symptom of thyroid cancer is a painless lump or swelling that develops in your neck.
Other symptoms only tend to occur after the condition has reached an advanced stage and may include:
- unexplained hoarseness
- difficulty breathing and swallowing
- pain in your neck
Read more about the symptoms of thyroid cancer.
The thyroid gland
The thyroid gland consists of two lobes located on either side of the windpipe. Its main purpose is to release hormones (chemicals that have powerful effects on many different functions of the human body).
The thyroid gland releases three separate hormones. They are:
- triiodothyronine, known as T3
- thyroxine, known as T4
- calcitonin
The T3 and T4 hormones help regulate the body’s metabolic rate (the rate at which the various processes in the body work, such as how quickly calories are burnt).
Excess T3 and T4 will make you feel overactive and you may lose weight. If you do not have enough of these hormones you will feel sluggish and you may gain weight.
Calcitonin helps control blood calcium levels. Calcium is a mineral that performs a number of important functions, such as building strong bones.
Calcitonin is not essential for maintaining good health because your body also has other ways of controlling calcium.
Types of thyroid cancer
There are four main types of thyroid cancer. They are:
- papillary carcinoma – this is the most common type, accounting for four out of five cases; it usually affects people under 40 years of age, particularly women
- follicular carcinoma – accounts for around one in 10 cases of thyroid cancer and tends to affect older adults
- medullary thyroid carcinoma – accounts for around one in 20 cases; unlike the other types of thyroid cancer, medullary thyroid carcinoma can run in families
- anaplastic thyroid carcinoma – is the rarest and most aggressive type of thyroid cancer, accounting for one in 100 cases; most cases affect older people aged 60-80 years
Papillary and follicular carcinomas are sometimes known as differentiated thyroid cancers (DTCs), and they are often treated in the same way.
What causes thyroid cancer?
In most cases, the cause of thyroid cancer is unknown. However, there are risk factors that can increase your chances of developing the condition.
Risk factors for thyroid cancer include:
- having a benign (non-cancerous) thyroid condition
- inheriting a faulty gene (in the case of medullary thyroid cancer)
- radiation exposure
Read more about the causes of thyroid cancer.
Diagnosing thyroid cancer
Your GP will examine your neck and ask whether you have any associated symptoms, such as unexplained hoarseness.
The next step will be to check whether the swelling in your neck is being caused by other thyroid problems. This will involve having a type of blood test, known as a thyroid function test, to measure the hormone levels in your blood.
Fine-needle aspiration cytology (FNAC) is the next stage in diagnosing thyroid cancer. Further testing may be required if the FNAC results are inconclusive, or if more information is needed to make your treatment more effective.
Read more about how thyroid cancer is diagnosed.
Treating thyroid cancer
Your recommended treatment plan will depend on the type and grade of your cancer, and if a complete cure is realistically achievable.
Most differentiated thyroid cancers (DTCs) – papillary and follicular carcinomas – and some medullary thyroid carcinomas are thought to have a good prospect of achieving a cure.
DTCs are treated using a combination of surgery to remove the thyroid gland (thyroidectomy), and a type of radiotherapy that destroys any remaining cancer cells and prevents the thyroid cancer returning.
Medullary thyroid carcinomas tend to spread faster than DTCs, so it may be necessary to remove any nearby lymph nodes as well as your thyroid gland. Lymph nodes are small, oval-shaped glands that remove unwanted bacteria and particles from the body. Radiotherapy iodine treatment is not used because it is ineffective in treating this type of thyroid cancer.
Read more about treating thyroid cancer.
Recurrence
Cancerous cells will return in an estimated 5-20% of people with a history of thyroid cancer. Approximately 10-15% of people will experience a return of cancerous cells in other parts of their body, such as their bones.
Sometimes, cancerous cells can return many years after surgery and radioactive iodine treatment has been completed. Due to this risk, you will be asked to attend regular check-ups so any cancerous cells that do return can be quickly treated.
Read more about the complications of thyroid cancer.
Preventing thyroid cancer
From the available evidence, eating a healthy, balanced diet is the best way to avoid getting thyroid cancer and all other types of cancer.
A low-fat, high-fibre diet is recommended, with plenty of fresh fruit and vegetables (at least five portions a day) and wholegrains.
Outlook
The outlook for the differentiated thyroid cancers (DTCs) is very good. Most people (80-90%) will have a normal lifespan.
Papillary and follicular carcinomas tend to be slow-growing and relatively straightforward to treat (see above).
More than nine out of 10 people with papillary carcinoma will live for 10 or more years after diagnosis. More than eight out of 10 people with follicular thyroid cancer will live at least 10 years after being diagnosed.
Medullary thyroid carcinoma is harder to treat. This type of thyroid cancer does not respond to iodine treatment, so removing all of the cancerous cells can be difficult.
Survival rates for medullary thyroid carcinoma depend on the stage of the cancer when it was diagnosed. If diagnosed in its early stages, the outlook is excellent, with 97% of people living at least five years after diagnosis.
However, if medullary thyroid carcinoma is diagnosed after it has spread to other parts of the body, the outlook is poor – only one in four people live at least five years after diagnosis.
Due to its aggressive nature, the outlook for anaplastic thyroid carcinoma is very poor. Fewer than one in 10 people will live at least five years after being diagnosed, with the average survival time being eight months.