Core biopsy

A core biopsy is a needle procedure that takes small cylindrical samples of tissue from a breast lesion under local anaesthetic, usually guided by ultrasound or mammography, so that a pathologist can confirm whether the lesion is benign or cancerous.

A core biopsy is the standard way of getting a definite diagnosis for a breast lump or imaging finding that needs tissue sampling¹³. In UK practice, histological core biopsy has largely replaced fine-needle aspiration cytology (FNAC) for breast diagnosis. It is done under local anaesthetic, usually in the same visit as the imaging, and takes around 15–20 minutes². The result is available within a few working days.

Orientation Why you might be reading about this

You have probably been told that a core biopsy is needed, or you have just had one and want to understand what it means. The word “biopsy” is often the most stressful step in the breast clinic pathway — patients arrive worried, and most leave with a benign result. This page explains what a core biopsy is, how it is done, what it can and cannot tell you, and what the result means.

Related terms: Breast lump · Breast ultrasound · Mammogram · Triple assessment · DCIS · Invasive ductal carcinoma

The procedure How a core biopsy is done

The procedure uses a spring-loaded biopsy needle to take small cylindrical samples of tissue² — typically 3–6 cores for ultrasound-guided lump biopsy, and often 10 or more for stereotactic biopsy of microcalcifications, where vacuum-assisted devices are increasingly used (each a few millimetres long and roughly 1 mm thick) from the area being investigated. Each sample is called a core. The cores are then sent to the laboratory, where a pathologist examines them under a microscope.

The needle is positioned using imaging guidance — almost always either²:

• Ultrasound guidance — for lesions visible on ultrasound (most lumps, cysts, and many imaging findings). The radiologist or surgeon watches the needle on the ultrasound screen and steers it directly into the target.
• Mammography guidance (called stereotactic biopsy) — for lesions seen only on mammography, particularly microcalcifications. The patient is positioned with the breast compressed in a special biopsy machine, two angled mammogram views are taken, and the needle is guided to the lesion using the mathematics of the two views.
• MRI guidance — used less often, for lesions visible only on MRI.

Step-by-step, the procedure goes like this:

1. The skin over the lesion is cleaned with an antiseptic wipe.
2. Local anaesthetic is injected — first to numb the skin, then deeper to numb the path of the needle.
3. A small nick is made in the skin to allow the biopsy needle to pass through.
4. The needle is guided to the lesion under imaging.
5. The biopsy device is fired — a quick, audible “click” — and a core sample is captured. This is repeated several times to get enough tissue.
6. A small clip or marker is sometimes placed in the lesion at the end (especially if the lesion may be removed later, or if it is small and may shrink with treatment), so its position can be relocated on future imaging².
7. The needle is withdrawn and pressure is applied to the area for several minutes to reduce bruising.
8. A small dressing is applied. No stitches are needed.

The whole process takes 15–20 minutes from the time the skin is cleaned. The procedure itself is usually well tolerated; most patients describe pressure rather than pain after the local anaesthetic has taken effect.

What it shows What the result can tell you

The pathologist examines the cores and reports on:

• Whether the lesion is benign or malignant.
• The specific diagnosis — for example, fibroadenoma, fat necrosis, DCIS, invasive ductal carcinoma, invasive lobular carcinoma.
• Key features for treatment planning if the lesion is cancer — including the grade, the hormone-receptor status (oestrogen receptor, progesterone receptor), and HER2 status⁶.

These features all feed into the treatment plan that is then discussed at the multidisciplinary team meeting before any surgery is recommended⁶.

Accuracy How accurate is core biopsy?

Modern core biopsy is highly accurate⁴. A clear benign or malignant result, taken from a confirmed target under image guidance, is reliable and does not need to be repeated. The small percentage of “discordant” results — where the biopsy and the imaging do not match — are reviewed at the multidisciplinary team meeting and either re-biopsied or excised surgically for confirmation³.

A negative biopsy is reliable when the imaging and biopsy results agree. A negative biopsy on a lesion that looks suspicious on imaging triggers the same MDT review and a likely re-biopsy or excision³.

Afterwards After the biopsy

You leave with a small dressing, mild bruising, and instructions to take simple pain relief if needed. Complications are uncommon: bruising and mild discomfort are usual; infection (~0.01{nd}0.2%) and, very rarely, pneumothorax (~0.01{nd}0.3%, more often with posterior stereotactic biopsies) are discussed at consent. There are no restrictions on driving, working, or normal activity, though heavy upper-body exercise is best avoided for a couple of days.

The result is typically available within 1–2 weeks, depending on the laboratory and on whether further tests (for example receptor status) are needed. The result is usually given at a follow-up appointment so that any discussion of next steps can happen at the same visit.

At consultation What to discuss with your surgeon

Before the biopsy:

• Whether a clip or marker is being placed (it usually is).
• Whether you are on any blood-thinning medication (some need to be temporarily stopped).
• What the imaging is showing and why a biopsy is the right next step.

After the biopsy:

• The specific diagnosis and what it means for you.
• The next steps — whether monitoring, removal, or further investigation.
• The full plan, which is usually agreed at the multidisciplinary team meeting before any surgery.

Core biopsy is usually done as part of a one-stop clinic visit, so imaging and sampling can be completed in one appointment where that is clinically appropriate.

Resources Further reading

• NHS — Your breast screening results — overview of what a biopsy is and how results are given (in the screening context).
• NHS — Breast cancer in women: Diagnosis — patient guide to mammography, ultrasound, biopsy, and MRI.
• Breast Cancer Now — Screening, tests and scans — patient-focused guide written by a UK breast cancer charity.
• Breastory: One-stop breast clinic · Symptoms assessment