Core Needle Biopsy of the Breast

If other tests show you might have breast cancer, your doctor may refer you for a core needle biopsy. During this procedure, a doctor uses a wide, hollow needle to take out pieces of breast tissue from the area of concern that’s felt by the doctor or pinpointed on an imaging test.  

What is a core needle biopsy (CNB)?

In a core needle biopsy (CNB), the doctor uses a wide, hollow needle to take out pieces of breast tissue from a suspicious area the doctor has felt or has pinpointed on an imaging test. The needle may be attached to a spring-loaded tool called a biopsy gun that moves the needle in and out of the tissue quickly.

A small cylinder (core) of tissue (about 1/16- to 1/8-inch in diameter and about ½-inch long) is taken out in the needle. Several cores are often removed. 

illustration showing the needle insertion site of a core needle biopsy along with details of the core needle and area to be biopsied

The doctor doing the CNB may put the needle in place by feeling the lump. But usually the needle is put into the abnormal area using some type of imaging test to guide the needle into the right place. Some of the imaging tests a doctor may use include:

  • Ultrasound
  • MRI
  • CT scan
  • Mammogram

Special types of core needle biopsies

Stereotactic core needle biopsy

When a doctor uses digital mammogram pictures taken from different angles to pinpoint the biopsy site, it’s called a stereotactic core needle biopsy. A computer analyzes the x-rays of the breast and shows exactly where the needle tip needs to go in the abnormal area. This type of CNB is often used to biopsy suspicious microcalcifications (tiny calcium deposits) or small tumors that can’t be clearly seen on an ultrasound.

Vacuum-assisted core biopsy

This type of CNB is done with a vacuum-assisted device (VAD). A hollow probe is put through a small cut into the abnormal area of breast tissue. The doctor guides the probe into place using an imaging test. A cylinder of tissue is then suctioned into the probe, and a rotating knife inside the probe cuts the tissue sample from the rest of the breast. Several samples can be taken from the same cut. This method usually removes more tissue than core biopsy done with a regular needle.

What should you expect if you have a CNB?

During the CNB

A CNB is an outpatient procedure most often done in the doctor’s office with local anesthesia (you’re awake but your breast is numbed). The CNB procedure itself is very quick, though it may take more time if imaging tests are needed or one of the special types of CNB is used.

You may be sitting up for the biopsy, or, more commonly, you may lie face down on a special table with openings that your breasts fit into. You will have to be still while the biopsy is done.

For any type of CNB, a thin needle will be used to put in medicine to numb your skin. Then a small cut (about ¼ inch) will be made in the breast. The needle or probe is put into the breast tissue through this cut. You might feel pressure as the needle goes in. Again, imaging tests may be used to guide the needle to the right spot.

Sometimes a tiny marker is put into the area where the biopsy is done. This marker shows up on mammograms so the exact area can be located and watched closely in the future. You can’t feel or see it.

Once the tissue is removed the needle or probe is taken out. No stitches are needed. The area is covered with a sterile dressing. Pressure may be applied for a short time to help limit bleeding.

After the CNB

You may be told to limit strenuous activity for a day or so, but should be able to go back to your usual activities after that.

A CNB can cause some bruising, but usually it doesn’t leave scars inside or outside the breast. 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 a CNB show?

A doctor called a pathologist will look at the biopsy tissue and/or fluid under a microscope to find out if there are cancer cells in it. A CNB is likely to clearly show whether cancer is present, but it can still miss some cancers.

Ask your doctor when you can expect to get the results of your biopsy. If the results of the CNB 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. Stereotactic Breast Biopsy. June 11, 2015. Accessed at on June 1, 2016.

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

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