Thyroid Fine Needle Aspiration Biopsy (FNAB)

A header graphic for Throid Fine Neelde Aspiration Biopsy

Thyroid nodules are clumps of soft tissues within the thyroid gland that in rare cases are cancerous or interfere with the proper functioning of the thyroid. In such cases, the nodules need to be treated. At UVA, radiologists perform Fine Needle Aspiration Biopsy (FNAB), an image guided procedure to diagnose thyroid growths.

What Is Fine Needle Aspiration Biopsy (FNAB)?

Fine Needle Aspiration Biopsy (FNAB) may sound intimidating, but it’s a simple, safe, and effective procedure to determine the nature of a thyroid nodule. Thyroid nodules are clumps of soft tissue within the thyroid gland in the neck. Most thyroid nodules are benign(non-cancerous), but sometimes they can be malignant (cancerous). Nodules that are large, solid, or have calcifications may need a biopsy.

At the UVA Health System, FNAB is performed by radiologists, doctors who specialize in reading images and scans of the body who sometimes also perform minimally invasive procedures using medical imaging to provide real-time views inside their patients’ bodies.

A FNAB procedure is quick and simple: most of these procedures take no more than 10 or 15 minutes.

During the FNAB procedure, a radiologist uses ultrasound to capture a real-time image of the thyroid nodule. They then guide a very fine (thin) needle to the nodule and take a number of tissue samples, which help aid the accuracy of diagnosis. The needle is so thin that Lidocaine, a topical anesthetic, is the only anaesthesia used. Normally, there is minimal to no discomfort after the procedure, but some patients may experience pain and discomfort for about 48 hours after the biopsy. Any post-procedure discomfort is usually managed with over-the-counter pain medications.

After the procedure is finished, samples are sent to a lab where they are evaluated by doctors called pathologists who will determine the exact nature of the nodule.

Interpreting the Biopsy Results

FNAB results fall into 3 categories: benign, malignant, or indeterminate.

An infographic explaining the three different results one can get from a Fine Needle Aspiration Biopsy (FNAB): benign, malignant, indeterminate


Most biopsies result in a benign diagnosis. This means that the nodules are just growths, and are not cancerous or causing any hormonal imbalances. Benign thyroid nodules do not need treatment unless they cause symptoms such as difficulty swallowing or breathing.


5% of FNAB procedures result in a malignant diagnosis, which means the thyroid nodule is cancerous. Malignant nodules need further medical attention and in a malignant diagnosis, the thyroid may be treated with radiation or removed to ensure the cancer doesn’t spread to other parts of the body.


Sometimes, it is impossible for the pathologist to make a benign or malignant diagnosis, this is known as an indeterminate diagnosis. When it comes to diagnosing something as serious as cancer, it’s important that a correct diagnosis is made. In the case of an indeterminate diagnosis, the next step is usually one of the following: repeating the biopsy, following up with further imaging, or removing a portion of the thyroid for testing. With more information, it’s usually possible to make a concrete diagnosis. If the second diagnosis shows the nodule is benign, no further procedures are necessary. If it comes back malignant, the rest of the thyroid will need to be removed.

FNAB is one of the most accurate ways to diagnose thyroid nodules. If you think you or a loved one has thyroid nodules, contact your doctor or one of the professionals at the UVA Cancer Center today to start the screening process.

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