What Is Thyroid Cancer? What Causes Thyroid Cancer?

Thyroid cancer is a type of cancer that occurs in the cells of the thyroid. The thyroid is a butterfly-shaped gland located at the base of the neck. It produces hormones that regulate the heart rate, blood pressure, body temperature and weight.

Thyroid cancer is not common. However, thyroid cancer rates seem to be increasing. This may be the result of improvements in technology making it easier to detect the condition at an earlier stage. This allows the finding of small thyroid cancers that may not have been found previously.

Women are more likely to get thyroid cancer than men.

The thyroid gland

The main role of the thyroid gland 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)
• calcitonin

Thyroxine and triiodothyronine help regulate the speed of the body’s functions (metabolic rate). The metabolic rate influences many different bodily functions, from how fast the heart beats to how fast it can burn up calories.

Calcitonin helps control the levels of calcium in the 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.

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 are:

• Papillary thyroid cancer. It is the most common. Papillary thyroid cancer can occur at any age, but it is most commonly diagnosed in people ages 30 to 50. (An estimated 80% of all thyroid cancer cases).
• Follicular thyroid cancer. Follicular thyroid cancer also includes Hurthle cell cancer. Follicular thyroid cancer typically occurs in people older than 50. (An estimated 11% of all thyroid cancer cases).

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 include:

• Medullary cancer. Medullary thyroid cancer may be associated with inherited genetic syndromes that include tumors in other glands. Most medullary thyroid cancers are not associated with inherited genetic syndromes. (About 4% of all thyroid cancer cases).
• Anaplastic cancer. The anaplastic type of thyroid cancer is very rare, aggressive and very difficult to treat. Anaplastic thyroid cancer typically occurs in people age 60 or older. (Between 1 and 2% of all thyroid cancer cases).
• Thyroid lymphoma. Thyroid lymphoma begins in the immune system cells in the thyroid. Thyroid lymphoma is very rare. It occurs most often in adults age 70 or older. (Between 1 and 2% of all thyroid cancer cases).

These rarer types of thyroid cancer are usually more aggressive, with a higher 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. The prognosis for non-DTC types of thyroid cancer is less favorable. If a complete cure is not possible, treatment can help to control symptoms and delay the spread of the cancer for many years.

What are the symptoms of thyroid cancer?

A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor detect. For example, pain may be a symptom while a rash may be a sign.

Thyroid cancer causes few symptoms in its early stage. As thyroid cancer grows, it may cause:

• A lump that can be felt through the skin on the neck
• Changes to the voice, including increasing hoarseness
• Difficulty swallowing
• Difficulty breathing
• Pain in the neck and throat
• Swollen lymph nodes in the neck

It is recommended to seek medical advice if a swelling or lump develops in the front of the throat. It is unlikely to be the result of thyroid cancer because 95% of these types of swellings are non-cancerous.

Goitres

Non-cancerous swellings, known as goitres, can be caused by other, less serious problems with the thyroid gland.

What are the causes of thyroid cancer?

How does cancer begin?

Cancer begins with an alteration to the structure of DNA that is found in all human cells. This is known as a genetic mutation. The DNA provides the cells with a basic set of instructions, such as when to grow and when to reproduce. The mutation in the DNA changes these instructions, so the cells keep growing. This causes them to reproduce uncontrollably, producing a lump of tissue known as a tumor.

How does cancer spread?

Left untreated, cancer can grow and spread to the other parts of the body, usually through the lymphatic system. It is a series of glands that spread throughout the body. Once the cancer reaches the lymphatic system, it is capable of spreading to any other part of the body.

The most common types of thyroid cancer, the differentiated thyroid cancers (DTCs), spread much slower than other types of cancer. In most cases where a DTC is diagnosed, it is usually limited to the thyroid gland, or has only spread to nearby lymph nodes.

The rarer types of thyroid cancer are more aggressive and spread faster. By the time it has been diagnosed, medullary cancer has usually spread to a large number of lymph nodes. Anaplastic cancer usually spreads to the windpipe and, in some cases, the lungs.

What are the risk factors for thyroid cancer?

Radiation exposure

Exposure to radiation in childhood has been identified as one of the leading risk factors for thyroid cancer. Two types of radiation that are associated with thyroid cancer have been identified:

Nuclear: Radiation released by nuclear fall-out. It is a type of radioactive waste that is released during a nuclear explosion. It can occur from fallout from nuclear accidents or weapons testing releasing levels of nuclear waste into the atmosphere.

Past medical treatments: This type of radiation was often used in the past for medical treatments. From 1910 to 1960, the risks of radiation treatment were not properly understood. Most cases involved children who received radiation treatments to their neck.

Today, there are much stricter regulations regarding the medical use of radiation in order to prevent the risk.

Sex

Women are three times more likely to develop thyroid cancer than men. The reasons for this remain unclear. No evidence has been found to support that this may be due to the hormones released during a woman’s period or during pregnancy.

Health conditions

There are a number of health conditions that increase the risk of developing thyroid cancer. These conditions are:

• Cowden’s syndrome A rare genetic condition that causes abnormal growths to develop on the skin and inside the mouth and nose.
• Familial adenomatous polyposis A genetic condition that causes abnormal growths in the intestine.
• Hashimoto’s thyroiditis A genetic condition where the immune system attacks the thyroid gland.
• Thyroid adenoma A non-cancerous growth of the thyroid gland.

Abnormal genes

There are three well-defined inherited conditions associated with medullary thyroid cancer. The genes are known and people who are suspected to have these syndromes can be tested to see if they carry the faulty gene. These are:

• the familial medullary thyroid cancer (FMTC)
• the multiple endocrine neoplasia (MEN) syndrome type 2A
• the multiple endocrine neoplasia (MEN) syndrome type 2B

People with a close family member who has developed medullar cancer may be advised to undergo screening in order to check whether they have inherited any of these faulty genes. If the genes are found, the thyroid gland can be surgically removed as a precaution. This procedure is known as a prophylactic thyroidectomy.

How is thyroid cancer diagnosed?

If there are any of the possible symptoms of thyroid cancer, a physical examination of the neck will be carried out, as well as a review of any associated symptoms, such as unexplained hoarseness.

Doctors will check whether the swelling in the neck is caused by other problems with the thyroid. A thyroid function test will be carried out.

Thyroid function test

The most common cause of swelling in the neck is either an overactive or underactive thyroid gland. To confirm or rule out these conditions, a thyroid function test may be carried out.

This test measures the amount of certain types of hormones in the blood. An excessive amount of the two hormones that are produced by the thyroid gland, thyroxine and triiodothyronine, would indicate an underlying condition that is making the thyroid gland overactive.

If the thyroid gland is underactive, another gland, known as the pituitary gland, will produce a hormone called thyroid stimulating hormone (TSH).

Further testing will be required if the thyroid function test reveals that the thyroid gland is working normally.

Fine-needle aspiration cytology

Fine-needle aspiration cytology (FNAC) is the next stage in diagnosing thyroid cancer. It is usually carried out under local anesthetic. A small needle will be inserted into the lump in the neck. The needle is used to remove a small sample of cells which are then studied under a microscope. A FNAC can usually reveal whether or not any cancerous cells are present in the thyroid gland. If they are, it will determine the type of thyroid cancer.

Further testing

Further testing may be recommended if the results of the FNAC are inconclusive. These tests may include imaging tests such as ultrasound of the neck to look for enlarged lymph nodes, such as a CT or MRI scan.

What are the complications of thyroid cancer?

Thyroid cancer can come back

Despite treatment, thyroid cancer can return, even if the thyroid has been removed. An estimated 5 to 20% of people with a history of thyroid cancer will experience a return of cancerous cells in their neck. An estimated 10 to15% of people will experience a return of cancerous cells in other parts of their body, such as their bones. This could happen if microscopic cancer cells spread beyond the thyroid before it is removed. Thyroid cancer recurrence can occur decades after thyroid cancer treatment.

Thyroid cancer most often recurs in:

• Lymph nodes in the neck
• Other areas of the body (most often the lungs or the bones)
• Small pieces of thyroid tissue left behind during surgery

Thyroid cancer that recurs can be treated. Periodic blood tests or thyroid scans may be recommended to check for signs of a thyroid cancer recurrence. Two tests can check for the return of cancerous cells: thyroglobulin testing, and a radioactive iodine scan.

What is the treatment for thyroid cancer?

Thyroid cancer treatment options depend on the type and stage of the thyroid cancer, the patient´s overall health and preferences.

Surgery

Most people with thyroid cancer undergo surgery to remove all or most of the thyroid. Operations used to treat thyroid cancer include:

• Removing all or most of the thyroid (thyroidectomy). Surgery to remove the entire thyroid is the most common treatment for thyroid cancer. Sometimes it is called as a near-total thyroidectomy because the surgeon leaves small rims of thyroid tissue around the parathyroid glands to reduce the risk of parathyroid damage.
• Removing lymph nodes in the neck. When removing the thyroid, the surgeon may also remove enlarged lymph nodes from the neck and test them for cancer cells.

The operation usually will leave a small scar on the neck, but it will not be very noticeable. After a thyroidectomy, swallowing food may feel painful for a number of weeks. It may therefore be necessary to switch to a diet of soft food until the throat recovers from the surgery. Most people are well enough to leave hospital within three to five days of thyroid surgery. But rest is needed for two to three weeks, as well as avoiding any activities that could put a strain on the neck such as heavy lifting.

There is a risk of accidental damage to the nerves connected to the vocal cords, which can cause vocal cord paralysis, hoarseness, soft voice or difficulty breathing. Occasionally, the parathryoid glands can be affected during surgery. The parathryoid glands are located close to the thyroid gland, and help regulate the levels of calcium in the blood. This can cause a tingling sensation in the hands, fingers, lips and around the nose. Most people only need to take a short course of calcium supplements as, over time, the parathryoid glands will resume their normal function.

Thyroid hormone therapy

After thyroid cancer surgery, the thyroid hormone medication levothyroxine (Levothroid, Synthroid, others) will be prescribed for life. It supplies the missing hormone the thyroid would normally produce, and it suppresses the production of thyroid-stimulating hormone (TSH) in the pituitary gland. This will stop stimulation of any remaining cancer cells to grow.

Regular blood tests will be required in order to check that the right amount of hormones are received and to determine whether the dose needs to be adjusted. Once the right dose has been determined, there should not be any side effects.

Radioactive iodine

Radioactive iodine treatment uses large doses of a form of iodine that is radioactive. Radioactive iodine treatment is often used after thyroidectomy to kill any remaining healthy thyroid tissue, as well as microscopic areas of thyroid cancer that were not removed during surgery.

Radioactive iodine treatment comes as a capsule or liquid to swallow. The radioactive iodine is taken up primarily by thyroid cells and thyroid cancer cells. For that reason, there is a low risk of harming other cells in the body. Side effects may include: Nausea, dry mouth, dry eyes, altered sense of taste or smell, pain where thyroid cancer cells have spread, such as the neck or chest.

In the first few days after treatment, most of the radioactive iodine leaves the body in the urine. During that time, the patient will need to take precautions to protect other people from the radiation. For instance, it may be necessary to temporarily avoid close contact with other people, especially children and pregnant women.

Dietary recommendations: When receiving radioactive iodine treatment, the patient will be asked to eat a diet that is low in iodine because a high iodine diet can reduce the effectiveness of the treatment. It is recommended to:

• avoid all seafood
• limit consumption of dairy products
• avoid taking cough medicines or sea salt as both contain iodine
• do not eat glace and maraschino cherries, as they contain coloring (E127) that is known to be high in iodine

Eat plenty of fresh meat, fresh fruit and vegetables, and pasta and rice. They are all low in iodine.

Pregnancy and breastfeeding: Pregnant women should not have radioactive iodine treatment. Both women and men are required to use a reliable contraceptive for at least six months after receiving iodine treatment.

External radiation therapy

Radiation therapy can also be given externally using a machine that aims high-energy beams at precise points on the body. Called external beam radiation therapy, this treatment is typically administered a few minutes at a time, five days a week, over several weeks. Side effects of radiotherapy include nausea, vomiting, tiredness, pain on swallowing, and dry mouth. These side effects should pass two to three weeks after the radiotherapy has finished.

Chemotherapy

Chemotherapy is a drug treatment that uses chemicals to kill cancer cells. Chemotherapy is typically given as an infusion through a vein. The chemicals travel throughout the body, killing quickly growing cells, including cancer cells. Possible side effects of chemotherapy include: nausea, vomiting, tiredness, loss of appetite, hair loss, and mouth ulcers.

Clinical trials

Clinical trials are studies of new cancer treatments or new ways of using existing treatments. Enrolling in a clinical trial gives the chance to try out the latest in cancer treatment options. However, clinical trials cannot guarantee a cure.

Coping with thyroid cancer

A diagnosis of thyroid cancer can be terrifying and overwhelming. To find a way of coping with a cancer diagnosis, try to:

Find out all you can about thyroid cancer. Write down all the details of your thyroid cancer, such as the type, stage and treatment options. Find out for more sources of information.

Connect with other thyroid cancer survivors. You might find comfort in talking with people in your same situation. Find out about support groups.

Take care of your health. You can take steps to keep your body healthy during and after treatment. For instance, eat a healthy diet full of a variety of fruits and vegetables, get enough sleep each night and try to incorporate physical activity several times a week.

What is the prevention for thyroid cancer?

Precautionary removal of the thyroid gland: People testing positive for one of the genes that is known to cause medullary cancer may be advised to have their thyroid gland removed as a precaution. (Prophylactic thyroidectomy)

Diet: Available evidence suggests that eating a healthy balanced diet is the best way to prevent getting thyroid cancer and all other types of cancer.

A low-fat, high-fiber diet is recommended, with plenty of fresh fruit and vegetables (at least five portions a day) and wholegrain.

Prevention for people near nuclear power plants: Fallout from an accident at a nuclear power plant could cause thyroid cancer in people living nearby. Potassium iodide is a medication that blocks the effects of radiation on the thyroid. If an emergency were to occur, you and your family could take potassium iodide tablets to help prevent thyroid cancer. Contact your local emergency management department for more information.

Written by Stephanie Brunner (B.A.)

Copyright: Medical News Today