Thyroid Cancer

At a glance

Thyroid cancer is a malignant tumor that starts in the thyroid gland at the front of the neck.
The thyroid is a butterfly-shaped organ that makes the hormones controlling the body's metabolism.

It is the most common cancer in Korea.
And in the 2023 national cancer registry statistics, the 5-year relative survival rate is 100.2%.
That means survival is, in practice, no different from people of the same age in the general population.

It depends on the type

Thyroid cancer includes papillary, follicular, medullary and anaplastic (undifferentiated) carcinoma.
Most cases are papillary carcinoma, which tends to grow slowly.

But anaplastic carcinoma, which is rare, behaves completely differently,
and every case of it is classed as stage 4.

So the saying "thyroid cancer is a good cancer" is only half true.
Most cases do well, but it depends on the type and the situation.
For your own case, check the biopsy result with your medical team.

If you are reading this page

People who search for thyroid cancer usually fall into two groups.

1. A thyroid nodule was found at a health check-up — 90~95% of the nodules you can feel in the neck are not cancer. Read 'See a doctor if you have these symptoms' below first.
2. You have been diagnosed with thyroid cancer — 'How it is treated' and 'Hospital stay and surgery' will give you a picture of what comes next.

This page is reference information summarising official sources.
Always talk to a medical professional about diagnosis and treatment.

There are no symptoms early on

The National Cancer Information Center explains that early thyroid cancer usually causes no symptoms.

The most common sign is a painless nodule (lump) in the neck.
Because it does not hurt, it is often found by chance or at a check-up.

90~95% of nodules are not cancer

Let us say this first.
According to the National Cancer Information Center, of the thyroid nodules you can feel in the neck,
90~95% are benign, and only about 5~10% turn out to be cancer.

Being told that you have a nodule does not mean you have cancer.

But these cases do need checking

These are the situations the National Cancer Information Center lists as 'more likely to be cancer'.

• The nodule is large, or has suddenly grown recently
• You also feel short of breath or have trouble swallowing food
• Your voice has changed
• The nodule is stuck to nearby tissue and does not move
• The nodule feels hard
• The lymph nodes in the neck on the same side are swollen
• You can feel a nodule and have a family history

If any of these apply to you, please do not put off seeing a doctor.

Risk factors

These are the causes of thyroid cancer listed by the National Cancer Information Center.

• Radiation — the best proven risk factor, especially radiation treatment to the face or neck in childhood
• Genetic factors — familial thyroid cancer, familial adenomatous polyposis and others
• Existing thyroid disease (this area is debated)
• Hormonal factors, diet, obesity

Where to go first

For the thyroid, the department is endocrinology.
If there is no endocrinology clinic near you, many general internal medicine or ear, nose and throat (ENT) clinics
also perform thyroid ultrasound.

You do not need to start at a large hospital.
Thyroid nodules are very common, and most of them are benign.
A local clinic will often do the ultrasound and, if needed, take a cell sample on the spot.

After diagnosis

Once cancer is confirmed, you move on to the department that performs surgery.

• Thyroid and endocrine surgery / general surgery — performs the operation
• Ear, nose and throat (head and neck surgery) — in some hospitals thyroid surgery is done here
• Nuclear medicine — handles radioactive iodine treatment
• Endocrinology — adjusts hormone medicine and follows you up after surgery

Which department performs thyroid surgery differs from hospital to hospital.
In some it is surgery, in others it is ENT.
When you book, say you want "a consultation for thyroid cancer surgery" and they will point you to the right department.

Do I need a large hospital

Once cancer is diagnosed, you will move to a hospital that can operate.
That said, thyroid cancer surgery is also performed at many general hospitals.
It does not have to be a tertiary hospital.

If you go to a tertiary hospital, you need a referral letter (진료의뢰서) for national health insurance (건강보험) to apply.

What to bring with you:

• The ultrasound images and the radiology report
• The result of the cell test (fine needle aspiration)
• Blood test results (thyroid function levels)

You can look for local clinics and large hospitals together on the map.

First, one thing to know — the screening advice is different

For thyroid cancer, the advice is the opposite of other cancers.

The National Cancer Information Center says this.

"Routine screening for thyroid cancer in adults or children without symptoms
(clinical palpation, ultrasound) is not recommended."

Also, thyroid cancer is not part of the national cancer screening program (국가암검진).
(The 6 major cancers supported by the state are stomach, liver, lung, colorectal, breast and cervical cancer.)

Why is it not recommended.
Thyroid nodules are found very often as soon as ultrasound is used,
and a large share of them never cause any problem in a person's lifetime.
The burden of unnecessary tests and operations can outweigh the benefit of finding them.

When a consultation is still needed

The National Cancer Information Center says that if the following applies to you,
you can decide about screening after talking with a specialist.

• You have a family history of thyroid cancer
• You had radiation to the face and neck area as a baby or a child
• You feel anxious about it

The last item matters.
It does not mean "do not get tested". It means do not decide alone; talk it over with a doctor.

The tests

• Thyroid ultrasound — the National Cancer Information Center calls this the most important test among those that check the shape of a nodule. It looks at size, shape, margins and calcification.
• Fine needle aspiration cytology — a thin needle draws cells from the nodule. This is the most important test for diagnosing thyroid cancer. It is done while watching the ultrasound, and it is usually short and done in the outpatient clinic without anaesthesia.
• Blood test — checks thyroid function (hormone levels). But these levels are not used to diagnose cancer.
• CT · MRI — done in addition, when needed, to check how far the cancer has spread.

If you were told at the ultrasound "let us watch it", be sure to keep the follow-up date you were given.
That is the normal way to handle a nodule.

The National Cancer Information Center lists the treatments for thyroid cancer as
surgery, radioactive iodine treatment, thyroid hormone treatment, external radiation therapy and chemotherapy.

Surgery — how much is removed

• Lobectomy (removing half) — only the lobe with the cancer is removed. It is used for papillary carcinoma that has not progressed far, and for benign tumors.
• Total thyroidectomy — the whole gland is removed, including both lobes and the isthmus.
• Neck lymph node dissection — when the cancer has spread to lymph nodes, or that is suspected, the lymph nodes around the neck are removed as well.

In some cases half of the thyroid can be left in place.
Leaving half means some people never have to take hormone medicine for life, so the difference is large.
Which one it will be depends on the size and number of the tumors and whether they have spread.

Types of operation

• Standard open surgery — the usual method, with an incision at the front of the neck
• Endoscopic thyroidectomy — leaves no scar on the neck, but is only possible when the cancer is small and has not spread
• Robotic surgery — cosmetically good, but the National Cancer Information Center says it is generally not recommended for advanced thyroid cancer

Radioactive iodine treatment

This treatment removes cancer cells that may remain after surgery.

It uses the fact that thyroid cells take up iodine.
When you take radioactive iodine, it collects in thyroid cells and the radiation destroys them.

It is given to patients who had a total thyroidectomy and have a high chance of recurrence, and only for differentiated cancers.

Taking thyroid hormone medicine

It has two purposes.

1. To replace the hormone that the removed thyroid used to make
2. To suppress thyroid stimulating hormone and prevent the cancer coming back

Because of the second purpose, some people take the medicine even when their hormone level is not low.
Do not stop it or change the dose on your own.

Other treatments

• External radiation therapy — a local treatment given over 3~6 weeks.
• Chemotherapy — thyroid cancer responds poorly to chemotherapy drugs, so it is only considered when surgery and radioactive iodine treatment do not work.
• Targeted therapy — sorafenib and lenvatinib for differentiated cancers, vandetanib and cabozantinib for medullary cancer.

Which treatments you have, and in what order, differs from person to person.
Talk it through fully with your medical team before you decide.

It differs by hospital and by the patient's condition, but the flow is usually like this.

If you have a cell test (fine needle aspiration)

A thin needle draws cells out while the doctor watches the ultrasound.
It is usually short and done in the outpatient clinic without anaesthesia, and you go home the same day.
The result takes a few days.

If you have surgery

1. Tests before surgery — blood tests, an electrocardiogram, a chest X-ray and so on check that you can cope with the operation.
2. Surgery — how much is removed (half or all) and the method (open, endoscopic or robotic) are decided beforehand.
3. Recovery — there may be a period with a tube in the neck to drain collected fluid. The hospital stay is fairly short.
4. After discharge — the final biopsy result decides whether radioactive iodine treatment is needed.

If you have radioactive iodine treatment

Before treatment there is a period of eating food low in iodine (a low iodine diet).
You will avoid seaweeds such as sea mustard and kelp, and some other foods; the hospital gives you a list.

After the treatment there is a period when radiation comes out of your body, so
you have to keep your distance from other people for a set period.
Sometimes a hospital stay is needed. Check the schedule in advance and prepare.

Things to ask before surgery

They can be hard to bring up, but it is better to ask before the operation.

• Could my voice change? How long would that last?
• Will I have to take calcium medicine after surgery?
• Will I take thyroid hormone medicine for life? Can I avoid it if only half is removed?
• How big will the scar be, and how do I care for it?
• Will I need radioactive iodine treatment?

Good things to bring

• Your referral letter, ID, national health insurance card
• The ultrasound images and report, and the cell test result
• Blood test results (thyroid function levels)
• A list of the medicines you take

The length of stay and the procedure differ from hospital to hospital.
Ask the hospital where you will have surgery for the exact details.

Special cost-sharing for serious illness

If you are diagnosed with thyroid cancer, you can apply for the special cost-sharing program for serious illness (산정특례).
Once you are registered, your out-of-pocket cost for care related to that cancer drops a lot,
and this applies for a set period.

The hospital that issued your diagnosis certificate usually applies on your behalf.
If you do it yourself, submit the registration form to the National Health Insurance Service (국민건강보험공단).

Test costs before diagnosis are different

Thyroid cancer is not part of the national cancer screening program.
So thyroid ultrasound is not provided free the way other cancer screenings are.

• If it is done as part of medical care because you have symptoms or a nodule you can feel, national health insurance may cover it.
• If you have it only for screening purposes with no symptoms, you may have to pay yourself.
• It is sometimes included in a comprehensive check-up package.

If you want to know the cost, call the hospital you plan to visit and ask in advance.

Costs differ by type of operation

• For robotic surgery and endoscopic surgery, what national health insurance covers is different from standard open surgery.
• When you choose the method, ask about the cost as well. The difference can be large.

Other help

• Depending on your income, you may qualify for the medical cost support program for cancer patients.

Programmes and out-of-pocket rates change.
What follows is a summary as of the reference date, so before you apply, always
check the latest rules at the National Health Insurance Service.