Radiologist's dual role in breast cancer management

Dr Duane Chambers

Sunday, October 29, 2017

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BY now everyone should be aware of the role the radiologist plays in breast cancer screening through the interpretation of mammograms, breast ultrasounds and breast magnetic resonance imaging (MRI).

The radiologist is also involved in the next step of breast cancer management through the performance of image-guided percutaneous biopsies. What this simply means is that a radiologist uses X-rays, ultrasound or MRI to guide a needle or wire to a suspicious area of the breast where a small piece of tissue is then removed. Because this biopsy is done through the skin, it is called a percutaneous biopsy.

The advantages of a percutaneous biopsy over a surgical biopsy include less scarring, fewer complications, lower cost, and faster recovery. Widespread acceptance of percutaneous breast biopsy techniques represents the most significant practice-changing development in breast imaging. The radiologist now plays a vital role not only in the detection of breast disease, but the management of breast cancer.

Most image-guided biopsies are performed with either a spring-loaded or vacuum-assisted device. A wire may also be placed in a mass or cluster of calcification to guide a surgeon to the precise location he or she should cut out. This is called hook wire localisation and excision biopsy.

Before a biopsy is started, all patients should sign an informed consent. The potential risks of bleeding and infection are explained as well as the steps taken to prevent these risks from happening.

MR guided biopsy cannot be done in patients with implanted metallic or electronic devices, or in those patients with an allergy to the contrast used in the procedure or who have impaired kidney function. Claustrophobia and obesity can also prevent an MR biopsy, as the patient must be able to fit into and tolerate an enclosed space for a prolonged period.

All the benefits of biopsy, including avoidance of surgery if the biopsy results are benign or preoperative confirmation of malignancy, which allows for proper surgical planning, should be explained.

Patients are then cleaned and draped and the site of skin entry marked. Lidocaine one per cent is then infiltrated subdermally first and then into the fibroglandular tissue of the breast to anaesthetise the breast and minimise pain during the procedure.

Ultrasound-guided biopsy

This is the preferred method of biopsy once the suspicious lesion can be identified by ultrasound. The method allows for real-time visualisation of the target and the biopsy needle to ensure accuracy and speed.

There is no need for breast compression and the patient can assume more comfortable positions during the procedure. There is no ionising radiation.

A skin entry site is generally made one to two centimetres from the edge of a high-frequency linear ultrasound probe. The needle is then directed to the edge of the targeted lesion.

Care must be taken to ensure adequate tissue beyond the lesion. The inner needle is fired first. It contains a recessed sampling notch. A hollow cutting cannula fires over the notched needle, cutting off tissue. This procedure is repeated four to six times to obtain sufficient tissue for analysis.

Stereotactic biopsy

X-ray imaging is used to target the lesion, which primarily includes suspicious microcalcification, but also includes masses, asymmetries and areas of architectural distortion not seen on ultrasound.

Vacuum-assisted devices are now the standard choice for retrieving tissue samples during stereotactic biopsy. The technique employs computer-assisted needle placement. In most cases, a tissue marker is placed at the completion of the biopsy to identify the biopsy site.

The absence of stereotactic equipment in Jamaica necessitates using mammographically guided hook wire localisation to guide surgeons to the site of lesions not visible on ultrasound so that local excision can be achieved.

Hook wire localisation.

A mammogram of the excised tissue confirms the targeted lesion has been removed. Ideally, a clip should be left in the breast to mark the surgical site.

Magnetic resonance-guided biopsy

Breast MRI is highly sensitive and often detects cancers that are invisible on mammography and ultrasound. Recommended equipment includes a 1.5T magnet, a dedicated breast coil and a vacuum-assisted device.

The patient lies facedown with the breast in a biopsy grid. The lesion is localised on post-contrast MR images and the position within the breast is then calculated manually or with computer-aided detection systems relative to the grid.

After biopsy, the breast is compressed for five minutes to prevent bleeding.

Irrespective of the method utilised, image-guided percutaneous breast biopsy is a safe, accurate and cost-effective method of establishing a tissue diagnosis.

Dr Duane Chambers is a consultant radiologist and founding partner of Imaging and Intervention Associates located at shops 58 and 59 Kingston Mall, 8 Ocean Boulevard. He may be contacted through the office numbers 618-4346 or 967-7748.




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