THYROID CANCER

( By JASCAP )

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Symptoms & diagnosis

Symptoms of thyroid cancer

In most people cancer of the thyroid develops very slowly. The first sign is usually a painless lump in the neck which gradually gets bigger. Occasionally, a thyroid tumour may press on the gullet (oesophagus) or windpipe (trachea) and cause difficulty in swallowing or breathing.

Very rarely, the first symptoms may be caused by secondary tumours in the bones or lungs after the cancer has spread beyond the thyroid.

It is unusual for cancer of the thyroid to affect the production of thyroid hormones, so symptoms of an over- or under-active thyroid are rare.

If you notice a lump in your neck, or any of the above symptoms, you should see your doctor as soon as possible. However, most thyroid swellings (or goitres) are benign (non-cancerous).

How thyroid cancer is diagnosed

If you have symptoms that may be due to a thyroid cancer, you will usually begin by seeing your GP. They will do an examination and arrange any tests which may be necessary. If your GP thinks that cancer may be present, or is not sure what the problem is, they will refer you to a hospital for specialist advice and treatment.

The doctor at the hospital will ask you about your general health and any previous medical problems, before examining you.

Blood tests

Samples of blood will be taken to check your thyroid hormone and TSH levels. Your blood will also be tested to check your general health.

Fine-needle aspiration or biopsy

For a fine-needle aspiration or biopsy, a small needle is passed gently into the swelling in your neck. Sometimes the doctor will use an ultrasound scanner to help guide the needle to the right area. They will then take a sample of cells and examine this under a microscope to check whether there are cancer cells present.

Further tests for thyroid cancer

The specialist will want to do some further tests. These may include any of the following:

  • Surgical biopsy
  • Ultrasound thyroid scan
  • Thyroid radioisotope scan
  • CT scan
  • MRI scan
  • PET scan

Surgical biopsy

Sometimes it may be necessary to do a surgical biopsy, which is done under either a local or general anaesthetic. The doctor will make a small cut in the skin close to the thyroid, and remove a small sample of the thyroid gland. You may have a surgical biopsy if:

  • it is not possible to do a needle aspiration or biopsy
  • the needle aspiration does not collect enough cells
  • the doctor who looks at the cells under the microscope (a pathologist) is not able to be sure about whether cancer cells are present from the needle aspiration or biopsy sample.

Ultrasound thyroid scan

Sound waves are used to make up a picture of the inside of the neck and the thyroid.

Once you are lying comfortably on your back, a gel is spread over your neck. A small device like a microphone, which produces sound waves, is then rubbed over the area. The sound waves are changed into a picture by a computer and may show whether the lump is solid or just fluid in a cyst.

Thyroid radioisotope scan

For this test a small amount of a slightly radioactive liquid (technetium or iodine) is injected into a vein in your arm. After about 20 minutes you will be asked to lie on a couch and a machine called a gamma camera will be positioned over your neck.

Cancer cells do not usually absorb the radioactive liquid as well as normal thyroid cells, so the camera may be able to show any areas of cancer in the thyroid. These are called cold areas or cold nodules.

The scan itself is painless and the radioactive injection has no harmful side effects.

CT scan

A CT (computerised tomography) scan is a series of x-rays, which build up a three-dimensional picture of the inside of the body. This type of scan is sometimes used to help the doctors know exactly how the cancer is affecting you and can be good at detecting thyroid cancer if it has spread to the lungs. The scan is painless but takes 10–30 minutes.

CT scans expose you to a small amount of radiation, which will be very unlikely to harm you and will not harm anyone you come into contact with.

It is important that you aren’t given an injection of a dye during the CT scan. The dye allows particular areas to be seen more clearly and it is fairly common for injections to be given during this type of scan. However, the dye contains iodine and can affect the way that radioactive iodine works.

MRI scan

An MRI (magnetic resonance imaging) scan is similar to a CT scan, but uses magnetic fields instead of x-rays to build up a series of cross-sectional pictures of the body. MRI scans can be useful for seeing if the cancer has spread in the neck.

During the test you will be asked to lie very still on a couch inside a metal cylinder that is open at both ends. The whole test may take up to an hour and is painless – although the machine is very noisy. You will be given earplugs or headphones to wear.

The cylinder is a very powerful magnet, so before going into the room you should remove all metal belongings. You should also tell your doctor if you have ever worked with metal or in the metal industry, or if you have any metal inside your body (for example, a cardiac monitor, pacemaker, surgical clips, or bone pins). You may not be able to have an MRI because of the magnetic fields.

Some people are given an injection of dye into a vein in the arm, but this usually does not cause any discomfort.

You may feel claustrophobic inside the cylinder, but you may be able to take someone with you into the room to keep you company. It may also help to mention to the staff beforehand if you do not like enclosed spaces. They can then offer extra support during your test.

PET scan

PET (positron emission tomography) scans are a specialist type of scan and you may have to travel to another centre to have one. They are not always necessary but you can discuss with your doctor whether one would be useful in your case. They are sometimes used if other investigations are negative or if the thyroid cancer comes back.

A PET scan uses low-dose radioactive glucose (a type of sugar) to measure the activity of cells in different parts of the body. A very small amount of a mildly radioactive substance is injected into a vein, usually in your arm. A scan is then taken a couple of hours later. Areas of cancer are usually more active than surrounding tissue and show up on the scan.

Staging of thyroid cancer

The stage of a cancer is a term used to describe its size and whether it has spread beyond its original site. Knowing the particular type and the stage of the thyroid cancer helps the doctors to decide on the most appropriate treatment.

Generally cancers are divided into four stages: small and localised (stage one); spread into surrounding structures (stages two or three); or spread into other parts of the body (stage four). If the cancer has spread to distant parts of the body this is known as secondary cancer (or metastatic cancer). Thyroid cancer is also staged according to the different types and the age of the person. The different staging systems are described below.

Papillary & follicular thyroid cancer in people under 45

Stage 1 The tumour can be of any size and nearby lymph nodes may also be affected, but there is no spread of the cancer to other parts of the body.

Stage 2 A tumour of any size that has spread to other parts of the body, such as the bones or lungs.

There is no stage 3 or 4 for these patients.

Papillary or follicular thyroid cancer in people aged 45 & over, & medullary cancer

  • Stage 1 The tumour is no bigger than 2cm in size and is contained within the thyroid gland. There has been no spread to either the lymph nodes or other parts of the body.
  • Stage 2 The tumour is contained within the thyroid gland and is between 2 and 4cm in size. There has still been no spread of the cancer to lymph nodes or other parts of the body.
  • Stage 3 The tumour is bigger than 4cm in size and is contained within the thyroid gland. Or, the tumour is of any size and has spread just outside the gland or to nearby lymph nodes in the neck.
  • Stage 4A The tumour may be any size and has spread into surrounding parts of the neck (such as the muscles, nerves or blood vessels) and/or to lymph nodes in the neck or the upper chest.
  • Stage 4B The tumour may be of any size and has spread to neck tissues near the backbone or around the upper neck or chest. The cancer may also have spread to lymph nodes.
  • Stage 4C The cancer has spread to other parts of the body, such as the lung or bone.

Anaplastic thyroid cancer

Everyone with anaplastic thyroid cancer is considered to have stage 4 disease. This stage is divided into three, depending upon how far the cancer has spread.

  • Stage 4A The tumour is of any size and contained within the thyroid gland. Lymph nodes may also be affected, but the cancer has not spread to other parts of the body.
  • Stage 4B The tumour is of any size and it has begun to spread into the soft tissues of the neck. Lymph nodes may also be affected, but the cancer has not spread to other parts of the body.
  • Stage 4C The cancer has spread to other parts of the body, such as the lung or bones.

TNM staging

Your doctors may also describe your thyroid cancer using the TNM staging system.

T describes the size of the tumour. There are four main stages ranging from T1 – T4.

N describes whether the cancer has spread to the lymph nodes close to the thyroid gland. There are two stages: in N0 there is no sign of cancer in the lymph glands; in N1 there are cancer cells in the lymph glands.

M describes whether the cancer has spread to another part of the body, such as the lungs or the bones (secondary or metastatic cancer). There are two stages: M0 is where there are no metastases; M1 is where there are metastases.

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