Fine Needle Aspiration (FNA) Biopsy of the Thyroid

Mature Woman at doctors office. Doctor is doing an external gland exam, touching her glands with hands, using latex gloves.
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The most common method for evaluation of a suspicious thyroid nodule or mass is a technique known as fine needle aspiration biopsy, abbreviated as FNA.

In an FNA, a very fine, thin needle is inserted into your thyroid, to aspirate (or "suction out") cells and/or fluid from your thyroid nodule or mass into the needle. The sample obtained can then be evaluated for the presence of cancerous cells.

How Does FNA Differ From Needle Core Biopsy?

In a needle core biopsy, a thicker, large needle is used to obtain a "core" tissue sample for analysis, and the larger sample that can be recut for smaller samples that can be sent out for further analysis. Needle biopsies are typically done using local anesthesia, and these procedures have a slightly greater risk of bleeding associated with them, so they are more often done by a surgeon in outpatient or ambulatory surgical facilities.

If an HMO or community does not have practitioners with expertise in performing FNA, or there are not cytopathologists available to do the unique form of interpretation needed for FNA results, patients are likelier to have a core needle biopsy, as this procedure, while more invasive for patients, requires less skill to obtain a valid sample, and less skill for pathologists to read and interpret.

Who Should Perform an FNA?

Typically, FNAs are done by endocrinologists, cytopathologists, or surgeons. The cells are studied and assessed by a cytopathologist.

Make sure that the practitioner has extensive experience in doing fine needle aspirations. Ask how many aspirations the practitioner does each month, and ask their "unsatisfactory" or "inconclusive" specimens rate. Don't always assume an endocrinologist is particularly skilled in this technique - he or she may not regularly perform this procedure.

The rate of non-diagnostic or unsatisfactory specimens — samples that cannot be used for laboratory assessment, and must be redone — can be high for some less experienced practitioners. Yolanda Oertel, M.D., a cytopathologist from the Washington Hospital Center who spoke about FNA at a Thyroid Cancer Survivor's Association (ThyCa) Conference in Washington, DC, cautions patients to find out the rate at the facility where their aspiration is taking place. The average can run from 5 to 15 percent. Dr. Oertel, whose practice focuses on thyroid and breast aspirations, and who aspirates approximately 90 thyroids each month, has a "non-diagnostic" rate is less than 0.5 percent.

Note: a special test is available on FNA biopsy results, called the Afirma Thyroid Analysis, from Veracyte, that eliminates the majority of non-diagnostic, indeterminate, or inconclusive FNA results. The test must be arranged to be performed as part of the biopsy process.

Where Is an FNA Performed?

Many FNAs are performed in a doctor's office, although some might be done as outpatient surgery.

Dr. Oertel, however, recommends that patients not get an FNA outside a hospital setting. While the procedure is generally safe, and things seldom go wrong, there is a very small risk of hemorrhage, but that could be quickly treated in a hospital setting.

What Is an Ultrasound-Guided FNA?

When a nodule is palpable - meaning, you can feel it with your hand - most practitioners don't need to use ultrasound to guide the FNA process.

Some nodules are very low-lying or can only be felt when you are swallowing, or can't be felt but were picked up by ultrasound, cat scan or MRI. In these cases, a practitioner may use ultrasound to ensure that the FNA is accurately performed.

Associated Risks

Thyroid FNA is generally considered safe, and almost never results in any complications.

Will It Hurt?

That depends on the skill of the practitioner, your own perceptions of pain. Some practitioners will use lidocaine, a local anesthetic, to numb the injection site. But patients complain that this can hurt more than the actual FNA procedure. Other practitioners don't use anesthetic. At a ThyCa conference, Dr. Oertel explained that she does not use an anesthetic, she prefers to use an ice pack to numb the skin. Her rationale: an anesthetic needle creates a lump and swelling around the injection site that can interfere with the ability to get an accurate sample.

Pain and Recovery

You might have slight pain with some swelling and bruising at the injection locations and possibly slight discomfort in swallowing. Ask your doctor about recommendations regarding post-FNA pain medication - many recommend taking acetaminophen or ibuprofen as directed to minimize any residual discomfort.

Can You Go Back to Work?

Most people are comfortable enough to go back to work the same day or the next day after having an FNA.
But you should avoid vigorous physical activity and sports for approximately 24 hours after the FNA.

Results to Expect

A nodule is more likely to be cancerous if it has certain risk factors:

  • Larger nodules: over 4 centimeters are more likely to be cancerous than nodules less than 4 centimeters
  • Men's nodules are more likely to be cancerous than women's nodules, however, nodules in pregnant women are more likely to be cancerous than nodules in a non-pregnant woman
  • A solitary nodule is more likely to be cancerous than nodules found in a "multinodular" thyroid
  • Nodules in a person younger than 20 or older than 70
  • History of external neck irradiation during childhood
  • "Cold" characterization on ultrasound, meaning the nodule does not absorb iodine or make thyroid hormone

Ultimately, however, approximately 5 percent of all thyroid nodules are cancerous.

What If It's Benign?

If you have a benign nodule, your doctor will likely treat the nodule. For more information, learn about thyroid nodules, lumps, and goiters as your starting point.

What If It's Malignant/Cancerous?

If you are diagnosed with thyroid cancer, your first stop should be the following article, an introduction to thyroid cancer, which is a good starting point for information about thyroid cancer, including papillary, follicular, medullary, and anaplastic cancer, including support groups and follow-up treatments. Your next step should be to join the Thyroid Cancer Survivor's Association, and to take advantage of their many patient support services.

What If It's Inconclusive or Indeterminate?

If a nodule is inconclusive, in the past, physicians have recommended surgery to remove all or part of the thyroid. Only 20 to 30% of inconclusive or indeterminate nodules are cancerous, however. This results in many unnecessary surgeries, along with lifelong hypothyroidism for many of those patients post-surgery. A test released in 2011, the Afirma Thyroid FNA Analysis process, developed by Veracyte, prevents inconclusive/indeterminate results for nodules, thereby offering more definitive FNA results, and preventing the need for surgery in the estimated 70 to 80 percent of patients who have inconclusive/indeterminate nodules, but no cancer.

Can You Have a False Diagnosis?

False results, such as false negatives showing your FNA results are benign when they are actually cancerous, or false positives showing a benign nodule as malignant, are more common than you think. Some experts estimate that an average of approximately 2 to 4 percent of all FNAs may be false results.

A Word From Verywell

If you have inconclusive or indeterminate findings and have not had the FNA tested using the Afirma Thyroid FNA Analysis process, you may want to have that test done to assess the nodule definitively before undergoing surgery.

If you have a negative result but have risk factors for or family history of thyroid cancer, in particular, you should consider getting a second opinion on your FNA. And, if you have a positive result indicating cancer, a second opinion is also important. 

You may feel uncomfortable about mentioning this to your doctor, or feel that it will be perceived negatively by your doctor, but, as Dr. Oertel said in her presentation to the ThyCa conference, "Get a second opinion. My ego will recover, but you might not!"

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Article Sources
  • Dr. Yolanda Oertel, Thyroid Cancer Survivor's Association Conference.