Thyroid fine needle aspiration (FNA)

Authors: Prof Stacy Goergen*
                            Prof Rob Gibson *

What is a Thyroid Fine Needle Aspiration (FNA)?

The thyroid is a soft gland in the front of the neck, in front of the trachea, or ‘windpipe’. It has two lobes (rounded divisions or sections), each about the size of a small egg, joined by a thin bridge of tissue called the ‘isthmus’ of the thyroid.

The thyroid gland is important, because it produces hormones that control metabolism, or the rate at which the body uses fuel. A fine needle aspiration (FNA) is a test that samples a small amount of tissue from the thyroid with a very thin (or ‘fine’) needle.

Why would my doctor refer me to have this procedure?

The most common reason for people to have thyroid FNA is to find out the cause of a thyroid lump (also called a ‘nodule’). The nodule might be something that you or your doctor have noticed because:

• You can see or feel a lump in the front of the neck in the area of the thyroid.
• You have general swelling in the thyroid area and your doctor sent you to have an ultrasound examination that showed one or more nodules in the gland.
• You had a thyroid problem detected while having a scanning (or imaging) test for other reasons.

The most common tests that show thyroid nodules are:

• ultrasound of the neck;
• computed tomography (CT) scanning that includes the neck or PET CT scanning of the whole body;
• nuclear medicine scanning of the thyroid.

In all of these cases, thyroid FNA is carried out to discover the cause for one or more nodules in the gland. Thyroid nodules are extremely common, being found on ultrasound in up to approximately 50% of adults. Palpable nodules (nodules that can be felt) are much less common, being present in approximately 5% of women and 1% of men.

Nodules are generally nothing to worry about and are more common in people born and raised in areas a long way from the coast, where the soil tends to be deficient in iodine. People living in these areas may have an iodine deficient diet. Iodine deficiency can make the thyroid gland get bigger (called a ‘goitre’). In some cases, this enlargement is a result of growth of one or more nodules in the gland.

Much less often, a nodule or nodules in the thyroid gland is a result of cancer. Most thyroid cancers have an excellent outcome if they are diagnosed and treated early. The reason for carrying out thyroid FNA in most cases is to confirm that the nodule or nodules in your thyroid are not a result of cancer.

How do I prepare for a thyroid FNA?

A thyroid FNA is a ‘day procedure’ for most people. It takes up to half an hour, followed by a short period afterwards when you will be watched until you have recovered and can leave the hospital or radiology practice. You are generally allowed to resume normal, but non-strenuous, activities for the rest of the day.

You can eat and drink normally before and after the procedure. You will not require a general anaesthetic where you would be asleep, although you may be given local anaesthetic to numb the area of the skin where the FNA needle is inserted.

When you make your appointment for the thyroid FNA, you need to let the hospital radiology clinic or department know if you are taking any blood thinning medication, such as warfarin, clopidogrel, dabigatran, prasugrel, dipyridamole or asantin (for more information about these medications, go to NPS: http://www.nps.org.au/medicines).

Blood thinning medications will need to be stopped for a period of days, or your normal dose reduced, before this procedure is carried out. It is very important that you do not stop any of these medications or change the dose without consulting both your own doctor and the hospital or radiology clinic where you will have the FNA. They will give you specific instructions about when to stop and restart the medication. These drugs are usually prescribed to prevent stroke or heart attack, so it is very important that you do not stop taking them without being instructed to do so by your doctor or the radiology practice, or both. Aspirin is usually not stopped.

A blood test may be required to check your blood clotting on the day of the procedure.

Continue with pain medication and other medications as usual.

It is important to take any previous scans or your thyroid that you have in your possession. The FNA will be carried out using ultrasound to guide placement of the needle within the thyroid gland.

What happens during a thyroid FNA?

An ultrasound machine will be used to locate the nodule or nodules to be sampled and show images or pictures of the nodule or nodules onto a screen.

The ultrasound will be carried out by a technologist (ultrasonographer or sonographer) or a radiologist (specialist doctor), or both.

The FNA procedure will then be explained to you. Instructions about what you can and cannot do after the procedure will be given to you at this time as well. You will be asked to sign a form indicating that you understand what will happen, the small risks involved, and that you agree to have the procedure done. The explanation will generally be provided by the doctor carrying out the procedure. You will have the opportunity to ask any questions at this time.

You will generally be lying on an examination couch for the procedure.

Your neck will be washed with antiseptic.

Sometimes, local anaesthetic is injected to make the skin numb before FNA is carried out. A very small needle will be guided into the thyroid nodule with the assistance of ultrasound images, so that the needle position can be seen. Once in the nodule, the needle will be ‘jiggled’ a few millimetres back and forth in order to take a sample of the tissue in the nodule, and then the needle will be removed.Very often, a technologist (called a cytology technologist) or a specialist doctor (a cytologist or pathologist) is present during the procedure and looks at the tissue sample through a microscope to see if enough tissue has been removed to make an accurate diagnosis of the nodule. Very often, the needle will need to be inserted and tissue samples removed two or three times until enough tissue to enable a proper study of the nodule is obtained. If you have more than one thyroid nodule, this procedure may need to be repeated for each nodule.

The procedure is then over. The needle puncture site in your neck will be compressed (pressure put on the site to stop any bleeding) for a couple of minutes by the doctor who did the FNA or a nurse who assists the doctor. An ice pack may be put on your neck to help reduce swelling and bleeding. You may be taken from the ultrasound room into an observation area for a short time to ensure that you are well enough to go home.

You should have been given instructions about what to do and what not to do after the FNA before you leave the hospital or radiology practice where you have had the procedure carried out. Even if a cytology technologist or pathologist is present for the procedure and looks at the samples under the microscope, the final answer about what the nodule is will generally not be ready for a few days. A full report will be sent by the pathologist to your doctor, who will discuss what it means with you.

Are there any after effects of a thyroid FNA?

It is common to have some pain, swelling and even a little bruise where the needle was inserted into your neck. Simple pain medication available from the chemist, such as panadol or panadeine, can be taken for this. Pain and swelling should be minimal after 48 hours.

It is important to avoid strenuous activity, particularly activity that involves bending over, straining (like lifting weights) or working over your head (like hanging out washing), as all of these activities can increase the chance of internal bleeding into the thyroid gland.

It is uncommon to have any change in your voice, severe pain, general neck swelling, or difficulty breathing or swallowing after a thyroid FNA. If any of these things happens, you should phone the hospital or radiology practice where the procedure was carried out and let them know.

If you are experiencing difficulty breathing after the procedure, you should go immediately to the nearest hospital emergency department.

How long does a thyroid FNA take?

The entire procedure takes approximately half an hour and you may be observed for a short time afterwards.

What are the risks of a thyroid FNA?

FNA is a very safe procedure and is considered very low risk for most people, because the needle that is used is so small.

There are two reasonably common risks and several rare risks that you should know about. The most common risk is an uncertain diagnosis, even after the tissue sample is looked at thoroughly by the pathologist. This happens up to 20% of the time.

The second most common risk is bleeding at the site of the FNA. This happens to approximately 1 in 10 people, and generally produces some local pain, tenderness and a lump. Simple pain medication available at the chemist (paracetamol) is generally sufficient to help the pain and it settles with the swelling over a few days. It is best to avoid aspirin for pain relief unless you are taking this daily for other reasons. Aspirin makes it harder for blood to clot, so paracetamol is better if you need to take something for pain after the thyroid FNA.

Major haemorrhage, enough to cause compression of your airway and problems breathing, is very rare (less than 1 in 1000 people). You need to go to a hospital emergency department immediately if this happens, and sometimes surgery is needed to stop the bleeding, but this too is very rare.

Rarer complications after thyroid FNA include:

• General swelling of the thyroid or neck area that is not painful and not related to bleeding.
• Change in voice (hoarseness). This can be a result of temporary injury of one of the nerves near the thyroid. It generally goes away over weeks to months when the nerve recovers.
• Difficulty swallowing.
• Temporarily abnormally increased thyroid function. This is thought to be a result of stimulation of the release of thyroid hormones by the FNA. It is very rare, but can produce excessive sweating or a ‘racing’ pulse or chest ‘palpitations’.

If any of these things happen to you, you should see your doctor.

What are the benefits of a thyroid FNA?

A FNA is a low-risk procedure that can be carried out on an otherwise healthy person in a short time as a day procedure. You can return to your normal activities within an hour of the procedure being carried out in most cases, provided these activities are not strenuous. In most cases, the FNA will tell your doctor whether or not the nodule is cancerous, but sometimes two FNA procedures are needed to finally decide this.

Who does the thyroid FNA?

A radiologist (specialist doctor) will carry out the placement of the needle into the nodule and removal of some thyroid tissue. A technologist (sonographer, ultrasonographer) may carry out the ultrasound that often happens just before the procedure. A cytology technologist or cytologist/pathologist (specialist doctor) will look at the cells that have been removed and provide a report about what the nodule is.

Where is a thyroid FNA done?

At a hospital radiology department or private radiology practice.

When can I expect the results of my thyroid FNA?

The pathology result generally takes a few days to be available to your doctor.
The time that it takes your doctor to receive a written report on the test or procedure you have had will vary, depending on:

• the urgency with which the result is needed;
• the complexity of the examination;
• whether more information is needed from your doctor before the examination can be interpreted by the specialist;
• whether you have had previous X-rays or other medical imaging that needs to be compared with this new test or procedure (this is commonly the case if you have a disease or condition that is being followed to assess your progress);
• how the report is conveyed from the practice or hospital to your doctor (in other words, email, fax or by post).

It is important that you discuss the results with the doctor who referred you, so that they can explain what the results mean for you.

Further information about thyroid FNA:

The radiologist may advise that an FNA is unnecessary, because the ultrasound findings indicate that it is highly unlikely to be a cancer. Sometimes the FNA needs to be postponed until further information is obtained from your doctor.

References

Tan, G.H. and H. Gharib, Thyroid incidentalomas: management approaches to nonpalpable nodules discovered incidentally on thyroid imaging. Ann Intern Med, 1997. 126(3): p. 226-31.
Liu, Y.I., et al., A Bayesian Network for Differentiating Benign From Malignant Thyroid Nodules Using Sonographic and Demographic Features. American Journal of Roentgenology, 2011. 196(5): p. W598-W605.
Cooper, D.S., et al., Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid, 2009. 19(11): p. 1167-214.
Polyzos, S.A. and A.D. Anastasilakis, Clinical complications following thyroid fine-needle biopsy: a systematic review. Clin Endocrinol (Oxf), 2009. 71(2): p. 157-65.
Polyzos, S.A., et al., Epidemiologic analysis of thyroid fine needle aspiration biopsies over a period of 18 years (1987-2004). Exp Clin Endocrinol Diabetes, 2008. 116(8): p. 496-500.

*The author has no conflict of interest with this topic.

Page last modified on 11/9/2018.