Fine Needle Aspiration Biopsy of the Breast

If other tests show you might have breast cancer, your doctor may refer you for a fine needle aspiration biopsy. During this procedure, a small amount of tissue is taken from the suspicious area, and checked for cancer cells.

What is an FNA breast biopsy?

In a fine needle aspiration (FNA) biopsy, the doctor uses a very thin, hollow needle attached to a syringe to withdraw (aspirate) a small amount of tissue from a suspicious area. The tissue is then checked under a microscope to see if there are cancer cells in it. The needle used for an FNA biopsy is thinner than the one used for blood tests.

If the area to be biopsied can be felt, the needle can be guided into it while the doctor is feeling it. 

illustration showing a fine needle aspiration using ultrasound including detail of the biopsy needle, area to be biopsied and the ultrasound transducer

If the lump can't be felt easily, the doctor might watch the needle on an ultrasound screen as it moves toward and into the mass. This is called an ultrasound-guided biopsy.

What should you expect if you have a FNA?

During an FNA

An FNA is an outpatient procedure most often done in the doctor’s office. Your doctor may or may not use a numbing medicine (called a local anesthetic). But, the needle used for the biopsy is so thin that getting an anesthetic could hurt more than the biopsy itself.

The biopsy itself only takes about 15 seconds for each sample. The entire procedure from start to finish generally takes around 20 to 30 minutes if ultrasound is used.

You’ll be laying on your back for the FNA. You will have to be still while it’s done.

You may feel some pressure from the ultrasound wand and as the needle is put in. Once the needle’s in the right place, the doctor will use the syringe to pull out a small amount of tissue and/or fluid. Then the needle is taken out and the area is covered with a sterile dressing or bandage.

After an FNA

Your doctor will tell you how to care for the biopsy site and what you can and can’t do while it heals. All biopsies can cause bleeding and can lead to swelling. This can make it seem like the breast lump is larger after the biopsy. Most often, this is nothing to worry about and the bleeding, bruising, and swelling go away over time.

What does an FNA show?

A doctor called a pathologist will look at the biopsy tissue or fluid under a microscope to find out if there are cancer cells in it.

  • If the fluid is clear, the lump is probably a cyst, and not cancer.
  • Bloody or cloudy fluid can mean either a cyst that’s not cancer or, very rarely, cancer.
  • If the lump is solid, the doctor will pull out small pieces of tissue.

The main advantages of FNA are that the skin doesn’t have to be cut, and in some cases it’s possible to make the diagnosis the same day.

An FNA biopsy is the easiest type of biopsy to have, but it can sometimes miss a cancer if the needle does not go into the cancer cells. Or there may not be enough cancer cells to do some of the other lab tests that are needed.

If the results of the FNA biopsy do not give a clear diagnosis, or your doctor still has concerns, you might need to have a second biopsy or a different type of biopsy.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Radiological Society of North America, Inc. Ultrasound-Guided Breast Biopsy. June 11, 2015. Accessed at www.radiologyinfo.org/en/info.cfm?pg=breastbius on June 1, 2016.

Last Medical Review: June 1, 2016 Last Revised: August 18, 2016

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