Fine Needle Aspiration (FNA) Biopsy of the Thyroid

A fine-needle aspiration (FNA) is a procedure that's used to sample cells from the thyroid gland for microscopic examination. This test is used in the diagnostic evaluation of a thyroid mass (also known as a nodule) or when there's a suspicion of thyroid cancer.

During an FNA, a very fine, thin needle is inserted into the thyroid gland to aspirate (remove) cells and/or fluid from the thyroid mass into the needle.

Purpose of Test

You may need to have a thyroid FNA if you have an enlarged thyroid gland or a thyroid mass. A thyroid mass may also be referred to as a nodule, growth, or lump.

A sample of thyroid cells obtained with an FNA can help healthcare providers evaluate the type of cells in a thyroid nodule, primarily to determine whether it is cancerous and, if so, how it can be treated.

You may need to have a thyroid FNA with ultrasound guidance, particularly if you have a small thyroid mass or if its location is difficult to access.

Limitations

Because a tiny sample of tissue is collected using an FNA, it is a diagnostic procedure, not a therapeutic one. It cannot remove or eliminate cancer from the thyroid gland.

A thyroid FNA technique does not provide enough information for your healthcare providers to determine whether cancer has spread to other regions of the thyroid or the neck. There is also a risk of false-negative results, which is a report of no cancer cells even if there is cancer in the thyroid gland.

In some cases, a needle core biopsy is used instead of FNA. The sample is obtained using a thicker needle than that used for FNA. The larger sample collected with a needle core biopsy can provide a better idea of the size and invasiveness of a tumor than an FNA, but with a higher chance of pain, bleeding, complications, and a longer recovery period.

Risks and Contraindications

FNA is considered a safe, minimally invasive procedure without serious risks.

Potential adverse effects include:

• There is a slight chance of persistent bleeding in or around your thyroid gland, particularly if you have a bleeding disorder or if you take blood thinners.
• Rarely, FNA can result in neck swelling, which may cause pain, trouble swallowing, or a hoarse voice.
• Another very uncommon complication is temporary, but potentially symptomatic disruption of thyroid hormone levels, resulting in either high or low thyroid hormone function.

If you experience neck swelling or symptoms of thyroid dysfunction, you should tell your healthcare provider immediately.

Before the Test

Before your thyroid FNA, you may need to have blood tests, which can include thyroid function tests and a basic metabolic panel. Your healthcare provider may tell you to adjust or stop taking some of your medications a few days before your procedure, including thyroid medications and blood thinners.

Timing

You can expect a thyroid FNA procedure to take approximately half an hour. Be sure to allow several hours for the test so that you can arrive in time to fill out paperwork and possibly stay after your procedure if your healthcare providers need to observe you.

Location

Thyroid FNAs can be performed in a doctor's office, at an outpatient surgery center, or in a radiology procedural suite. The healthcare system where you are seen likely has its own process in place for thyroid FNA.

What to Wear

You can wear anything comfortable to your procedure, but avoid any clothing that covers your neck. You may be asked to change into a gown for your procedure.

Food and Drink

Before your procedure, you can eat and drink whatever you normally would.

Cost and Health Insurance

The cost of a thyroid FNA is likely covered by your health insurance plan. Pre-authorization is often required for non-emergency procedures like FNA. You may be responsible for a portion of the cost or for a copay, and you can find out if any of the cost is your responsibility by checking with your health insurance carrier.

If you are paying for the test out-of-pocket, your cost can range between $400 and $1600. Ultrasound-guided FNA and the use of anesthetic medication are more likely to put the cost at the higher end.

What to Bring

When you go to have your test, you should bring a form of identification, your insurance information, and a means of payment for your portion of the cost. You should expect to be completely alert and able to drive and resume your regular activities after the procedure, so it is not required that you bring anyone with you.

During the Test

A physician will perform your thyroid FNA. It may be done by an endocrinologist, a surgeon, or a radiologist. A nurse or a technician will probably also be present to assist before, during, and after your procedure.

Pre-Test

Before your test, you will need to sign paperwork, which generally includes a consent form and authorization for payment. Soon after, you will be called in to prepare for your procedure. A nurse or technician will check your vital signs and may ask you to change into a gown.

Throughout the Test

Your healthcare provider may review your imaging tests and will feel your neck to locate your thyroid gland, as well as your thyroid mass if it is palpable (can be felt by touching your neck). If you have a mass that can't be easily palpated, your practitioner may use ultrasound during your procedure to help locate the mass.

Steps of your procedure:

• Your neck will be cleaned and sterilized.
• You may have an injection with a local anesthetic.
• You may be asked to turn your neck while you remain in a seated position or asked to lie down so that your healthcare provider can have the best access to your thyroid mass to obtain the sample.
• You may feel a slight pinch when your healthcare provider inserts the needle, and you should expect this sensation to last for less than a minute.

Once the needle is removed, you may need a small bandage over the puncture site on your neck.

Post-Test

Your healthcare provider or nurse will check on you and may want to observe you after your procedure to monitor for any side effects. If you have no side effects, you will be discharged and you can resume routine activities, including eating and drinking.

After the Test

In the first few days after your thyroid FNA, you might experience slight pain, swelling, or bruising near the injection site, and possibly slight discomfort when you swallow. You should avoid vigorous physical activity and sports for approximately 24 hours after your thyroid FNA, primarily to avoid any injury to your thyroid gland as it is healing.

Managing Side Effects

Your healthcare provider may recommend using ice or taking Tylenol (acetaminophen) to minimize your discomfort. You should not use non-steroidal antiinflammatories (NSAIDs) like Motrin or aspirin, because they can increase the risk of bleeding.

If you experience severe pain, swelling, a growing lump, a fever, or symptoms of hyperthyroidism or hypothyroidism, you should call your healthcare provider.

Interpreting Results

Your tissue sample will be interpreted by a pathologist, who will look at it under a microscope. The results may be available during your procedure, immediately afterward, or a couple of weeks later. This depends on factors such as whether the sample will be evaluated by an on-site lab or whether it needs to be sent to another facility, which can take longer.

There are several features that the pathologist will consider when examining your biopsy sample, including the presence of inflammatory cells, evidence of an infection, or thyroid cancer cells.

It is possible for the cells to be completely normal, suggesting a benign (noncancerous) lesion.

If you are diagnosed with thyroid cancer, the biopsy sample can help your healthcare provider determine which type of thyroid cancer you have:

• Papillary cancer
• Follicular cancer
• Medullary cancer
• Anaplastic cancer

These differ from each other in their microscopic appearance. For example, anaplastic thyroid cancer, one of the most aggressive thyroid tumor types, is characterized by poorly differentiated cells, which means that they do not appear like mature thyroid gland cells.

In some instances, a mass in the thyroid gland may be caused by metastasis (spread) of another tumor type.

Follow-Up

If you have evidence of cancer, based on the results of your thyroid FNA, you will likely need to have surgery, radiation, and/or chemotherapy.

If your FNA does not show signs of cancer, your healthcare providers will likely treat your thyroid condition with medication. However, they may continue to search for evidence of cancer if there is still a high suspicion that you could have thyroid cancer despite the negative FNA results. The next steps may include a more extensive biopsy or further diagnostic imaging tests.

A Word From Verywell

A biopsy is often considered the most definitive way to analyze thyroid tissue. If you are scheduled to have a thyroid FNA, you should know that this is a minimally invasive procedure with limited side effects. Be aware, however, that because it provides only a tiny sample of cells, the results of a thyroid FNA must be considered along with the results of all your other tests, including your thyroid hormone blood tests and diagnostic imaging examinations.