Thyroid cancer

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 cancer of the thyroid is a painless lump or swelling that develops in the neck.

Other symptoms only tend to occur after the condition has reached an advanced stage, and may include:

• unexplained hoarseness that lasts for more than a few weeks
• a sore throat or difficulty swallowing that doesn't get better 
• a lump elsewhere in your neck

It's important to remember that if you have a lump in your thyroid gland, it doesn't necessarily mean you have thyroid cancer. About 1 in 20 thyroid lumps are cancerous. 

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 body).

The thyroid gland releases three separate hormones:

• 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).

An excess of T3 and T4 will make you feel overactive and you may lose weight. If you don't have enough of these hormones, you'll 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 isn't 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 about 6 out of 10 (60%) cases; it usually affects people under the age of 40, particularly women
• follicular carcinoma – accounts for around 3 out of 20 (15%) cases of thyroid cancer and tends to affect older adults
• medullary thyroid carcinoma – accounts for between 5 and 8 out of every 100 diagnosed cases (5-8%); unlike the other types of thyroid cancer, medullary thyroid carcinoma can run in families 
• anaplastic thyroid carcinoma – this is the rarest and most aggressive type of thyroid cancer, accounting for less than 1 in 20 thyroid cancers; it usually affects older people over the age of 60 

Papillary and follicular carcinomas are sometimes known as differentiated thyroid cancers, and they're often treated in the same way.

How common is thyroid cancer?

Thyroid cancer is a rare form of cancer, accounting for less than 1% of all cancer cases in the UK. Each year, around 2,700 people are diagnosed with thyroid cancer in the UK.

It's most common in people aged 35 to 39 years and in those aged 70 years or over.

Women are two to three times more likely to develop thyroid cancer than men. It's unclear why this is, but it may be a result of the hormonal changes associated with the female reproductive system.

What causes thyroid cancer?

In most cases, the cause of thyroid cancer is unknown. However, certain things can increase your chances of developing the condition.

Risk factors for thyroid cancer include:

• having a benign (non-cancerous) thyroid condition
• having a family history of thyroid cancer (in the case of medullary thyroid cancer)
• having a bowel condition known as familial adenomatous polyposis
• acromegaly – a rare condition where the body produces too much growth hormone
• having a previous benign (non-cancerous) breast condition
• weight and height
• radiation exposure 

Read more about the causes of thyroid cancer.

Diagnosing thyroid cancer

A type of blood test known as a thyroid function test will measure the hormone levels in your blood and rule out or confirm other thyroid problems.

If nothing else seems to be causing the lump in your thyroid, fine-needle aspiration cytology (FNAC) is used.

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 whether a complete cure is realistically achievable.

Differentiated thyroid cancers (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.

Read more about treating thyroid cancer.

Recurrence

Cancerous cells will return in an estimated 5-20% of people with a history of thyroid cancer. In approximately 10-15% of people the cancerous cells will come back in other parts of their body, such as their bones.

Cancerous cells can sometimes return many years after surgery and radioactive iodine treatment has been completed. 

You'll be asked to attend regular check-ups so any cancerous cells that return can be treated quickly. 

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 that includes plenty of fresh fruit and vegetables (at least five portions a day) and whole grains.

Outlook

The outlook for differentiated thyroid cancers 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.

More than 9 out of 10 people with papillary carcinoma will live for 10 or more years after diagnosis. More than 8 out of 10 people with follicular thyroid cancer will live for at least 10 years after being diagnosed.

Medullary thyroid carcinoma is harder to treat. It doesn't 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, 97% of people live at least five years after diagnosis.

If medullary thyroid carcinoma is diagnosed after it has spread to other parts of the body, 1 in 4 people live at least five years after diagnosis.

Because of its aggressive nature, less than 1 in 10 people with anaplastic thyroid carcinoma will live at least five years after being diagnosed.