Fine Needle Aspiration Biopsy

Also known as: FNAB, ultrasound-guided fine needle aspiration biopsy

What is fine needle aspiration biopsy?

A biopsy is a medical procedure used to gather a sample of tissue from within the body. Typically, this is done to test the tissue to see if cancer might be present. A fine needle aspiration biopsy (FNAB) is performed by an interventional radiologist and uses a needle to gather the tissue sample. This makes it less invasive than other methods of biopsy. If you have thyroid nodules and your doctor wants to check for thyroid cancer, a FNAB of the thyroid may be recommended.

What happens during the treatment?

A FNAB is performed by a specialist known as an interventional radiologist. This professional will use ultrasound for guidance while injecting the fine needle into the neck to extract a small sample of tissue from the thyroid. The sample will then be tested in a laboratory for cancer or high levels of thyroid hormones.

Is any special preparation needed?

No special preparation is typically needed. Notify your doctor if you are taking any blood-thinning medications prior to the procedure.

What are the risk factors?

It’s normal for the injection site to be sore for a few days after the FNAB. Infection, bleeding, or swelling at the injection site are all potential risks.

Reviewed by: Alejandro Diaz, MD

This page was last updated on: September 16, 2025 12:53 PM