Overview 

The thyroid is an important, small butterfly-shaped gland in front of the windpipe. The thyroid produces hormones called thyroxine (T4) and triiodothyronine (T3) which play a role in metabolism, the speed at which body cells work. Within the body, T4 is converted to T3  to interact with cells and tissues.¹ The thyroid follicular cells are responsible for the production and secretion of thyroid hormones.

Thyroid cancer is rare and has approximately 3,900 people diagnosed in the UK yearly.  However, its incidence is increasing. It’s more common in women than men and has a high survival rate.² Follicular thyroid cancer is the second most common type of thyroid cancer, accounting for approximately 10-15% of cases.³

Causes of follicular thyroid cancer

Cancers occur because of the uncontrollable growth and reproduction of abnormal cells. Most cancers start as a result of gene changes. The abnormal cells are usually kept in check by tumour suppressor genes but; mutated versions of genes called oncogenes are responsible for this uncontrolled cell proliferation. 

Often, it isn’t clear why thyroid cancer develops. However, certain groups of people seem to be more susceptible to developing the disease. For example: ⁴

• Being overweight is more likely to result in cancer, including thyroid cancer, than maintaining a healthy weight
• Those assigned females at birth are more likely to develop the disease.
• Those that have non-cancerous thyroid disease like Hashimoto’s disease
• Those that have thyroid nodules
• People with a family history of the disease
• People who have been subjected to high doses of radiation, for example, people that received radiotherapy as a child. However, research suggests that regularly exposure to radiation in the workplace does not increase the risk of thyroid cancer
• People who have previously had cancer are more likely to get it again
• People who suffer from the autoimmune disorder systemic Lupus are slightly  more likely to develop thyroid cancer than those without the disorder

Signs and symptoms of follicular thyroid cancer

The symptoms of thyroid cancer are predominantly painless and most thyroid lumps are not cancerous. It’s important to get checked out by a doctor immediately if any of the symptoms are present to rule out any malignancies. Symptoms include:⁵

• A swelling or lump in the neck (these are usually painless)
• A persistent hoarse voice
• Trouble swallowing
• The feeling of pressure in the throat when swallowing
• Problems with breathing,
• especially when sleeping
• Pain in the front of the neck

Management and treatment for follicular thyroid cancer

In most cases, thyroid cancer has a high rate of curability.  As with all cancers, treatment options depend on the size of the cancer and whether or not it has spread. 

Surgery:

The most common treatment is to remove the thyroid through surgery. Part or all of the thyroid can be removed in a procedure called a total thyroidectomy (where all of the thyroid is removed) or a lobectomy/partial thyroidectomy (where the thyroid is partially removed).⁶ Total removal of the thyroid will result in having to take medication for the rest of a patient’s life because they can no longer produce the T4 and T3 hormones. For follicular thyroid cancer, taking the replacement hormones can reduce the chance of recurrence because they stop your body from producing another hormone called thyroid stimulating hormone (TSH) which can encourage follicular cancer cells to develop.⁷

Radioactive iodine treatment: 

For follicular and papillary thyroid cancer, radioactive iodine treatment is often effective. The thyroid normally absorbs iodine and uses it to make thyroid hormones. The radioactive iodine is usually taken in the form of a pill and circulates the body before being taken up by thyroid cells. The radiation then kills the cancer cells. 

This treatment option is often combined with surgery to kill any remaining cancer cells and can also be used if the cancer has spread. 

For some patients, treatment is a one-off. Others may need to have it repeated until there is no sign of cancer cells on their scans.⁸

Some preparation rules are important to follow before embarking on iodine treatment. These include:⁹

• Following a low-iodine diet before the treatment; this is to ensure that the thyroid cells are prepared to absorb the iodine when the treatment is administered
• Your thyroid needs to have high levels of TSH to allow the cancer cells to take up the treatment. This can be achieved by having an injection or stopping your thyroid hormone tablets

Although the radiation in the treatment does not harm the patient, the patient will be radioactive, so they must isolate themselves in the hospital for several days. 

Once a patient returns home, there are other precautions to take after radioactive treatment such as avoiding sexual contact and keeping your distance from other people for a couple of weeks. 

Chemotherapy:

Chemotherapy is not often used for thyroid cancer unless it has spread to other areas in the body. 

Targeted cancer drugs: 

The targeted cancer drugs work by targeting the differences in cancer cells that make them able to survive. Patients are more likely to be offered targeted drugs if radioactive iodine and surgery have not eliminated their cancer. 

Although targeted cancer drugs are not appropriate for all cancer types, they are used to treat follicular thyroid cancer. 

Tyrosine Kinase inhibitors (TKIs) work by blocking tyrosine kinase; this is involved in cell signalling and can control the growth of new cancerous cells. 

These drugs are even in tablet form and side effects can be challenging. However, a cancer nurse or medical professional would be the best person to advise patients on how to deal with the symptoms they may experience.¹⁰

FAQs

How is follicular thyroid cancer diagnosed?

When a patient visits their GP with symptoms indicative of thyroid cancer, they will have their neck examined so that the GP can feel for any lumps or swellings that might be present. They might also carry out blood tests to check thyroid hormone levels. 

If the GP thinks it is appropriate, the GP will refer the patient to a specialist. Here, an ultrasound is likely to be carried out on the neck area. This is to look for any lumps and to see if they are fluid-filled or solid. 

A needle biopsy is needed to diagnose thyroid cancer; this is when a small needle is inserted into the lump in the thyroid and fluid is removed. This fluid is then sampled in a laboratory to check if cancer cells are present. 

Scans such as MRI, PET and CT might also examine the size of the cancer and if it has spread to other areas of the body.¹¹

Can follicular thyroid cancer be prevented?

There is no single way to avoid follicular thyroid cancer but avoiding radiation exposure can lower the risk. Only 9% of thyroid cancers that occur in the UK are preventable.¹²

The best way to reduce your chances of getting cancer is to follow a healthy lifestyle. 

What are the risk factors of follicular thyroid cancer?

The risk factors of follicular thyroid cancer are:

• Being assigned female at birth
• High exposure to radiation
• A family history of the disease
• Having had cancer previously

How common is follicular thyroid cancer?

Follicular thyroid cancer is the second most common form of thyroid cancer.

The condition most frequently affects persons between the ages of 40 and 60, but younger people are now being affected by it more frequently than in the past. Between 2016-2018 there were 3865 new cases of thyroid cancer diagnosed.¹³

When should I see a doctor?

You should always see a doctor as soon as possible if there have been changes to your health recently.  The symptoms are less likely to be caused by cancer compared to benign conditions, but as with all cancers, the earlier it is diagnosed, the easier it is to treat. Several non-cancer thyroid conditions can cause a range of symptoms and complications and so any concerns should be evaluated by a doctor. 

Summary 

The thyroid gland in the neck produces hormones necessary for metabolism. Follicular thyroid cancer occurs in one of the follicular cells that make up the thyroid; the follicular cells. Symptoms include a lump and the feeling of pressure in the neck. This cancer has a high survival rate and the treatment options include surgery and radioactive iodine. It is unclear why follicular thyroid cancer occurs but high exposure to radiation increases the chance that it will develop and occurs more often in those assigned females at birth.