Fine Needle Aspiration (FNA) Biopsy of the Thyroid

A fine needle aspiration (FNA), used to sample thyroid gland cells, is the most common invasive method used in the diagnostic evaluation of a thyroid mass (also known as a nodule).

In an FNA, a very fine, thin needle is inserted into your thyroid gland to aspirate (remove) cells and/or fluid from your thyroid mass into the needle. The sample that is obtained can then be viewed under a microscope to look for the presence of cancerous cells.

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 thyroid mass may be solid or filled with fluid, and it generally differs in some way from the rest of your thyroid gland. It may be harder in texture, or it may have a distinct appearance on an imaging examination.

A sample of your thyroid cells obtained with an FNA can help your doctors 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 your FNA with ultrasound guidance, particularly if your thyroid mass is small or difficult to access.

In some cases, a needle core biopsy is instead used for this purpose. The sample is obtained using a thicker, large 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 can, but with a greater chance of pain, bleeding, and complications, and a longer recovery period.

Limitations

Because a tiny sample of tissue is collected using an FNA, it is a diagnostic procedure, not a therapeutic one. A tiny amount of cells is sampled, so a thyroid FNA cannot be used to remove or eliminate cancer from the thyroid gland.

The cells obtained using a thyroid FNA can be analyzed under a microscope, but the technique does not allow your doctors 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, indeed, cancer in the thyroid gland.

Risks and Contraindications

FNA is considered a safe, minimally invasive procedure without serious risks. 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 swelling of the neck, 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 thyroid dysfunction, you should tell your doctor 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 doctor 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 doctors 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 how much, 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 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 at that point.

Throughout the Test

Your doctor 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 be touching your neck). If you have a mass that can't be easily palpated, your doctor may use ultrasound during your procedure to help locate the mass.

Your neck will be cleaned and sterilized, and 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 doctor can have the best access to your thyroid mass to obtain the sample.

You may feel a slight pinch when your doctor inserts the needle, and you should expect this sensation to last for less than a minute.

Post-Test

After your procedure, you may need a small bandage over the puncture site on your neck. Your doctor or nurse will check on you and may want to observe you after your procedure to ensure that you are not experiencing any unwanted 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 doctor may recommend using ice or taking Tylenol (acetaminophen) or Motrin (ibuprofen) to minimize your discomfort.

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

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 largely on 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 or thyroid cancer cells.

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

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

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.

You may have inflammatory cells or evidence of an infection. And 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 doctors 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. 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.

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