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.

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.

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.

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.

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 (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.