Stereotactic breast biopsy

Stereotactic breast biopsy refers to obtaining a sample of breast tissue using mammographic guidance for targeting. It is the biopsy method of choice when the finding of interest is best seen on mammography, such as microcalcifications or architectural distortion.

Devices

Stereotactic devices differ by imaging modality (analog vs digital), calculation of coordinates (manual or digital), and type of needle (fine-needle aspiration biopsy or vacuum-assisted core needle biopsy).

Positioning

Patient position depends on the equipment. In the prone position, the patient lies face down on a special bed with the breast protruding through a hole in bed surface. However, in the sitting position, the patient is in front of the equipment and can see the needle.

The breast is placed in compression using special paddle with a central window and a mammogram is performed.

Targeting

Once the lesion is highlighted in the first mammogram, additional views are needed to triangulate the lesion in three-dimensional space. Traditionally, two additional projections are performed at +15 and -15 degrees. In the era of digital breast tomosynthesis, the lesion is located on a tomosynthesis slice obtained as part of the initial mammogram. The spatial coordinates of the lesion target are then calculated. With the breast still in compression, the cutaneous entry point is identified.

Vacuum-assisted core biopsy

First, local anaesthesia (1% lidocaine) is applied. The needle is then pushed to the target previously determined. The distance is confirmed through an additional acquisition and corrected if necessary.

Vacuum-assisted biopsy involves obtaining multiple tissue cores via a rotating 11-14 gauge needle while the machine applies suction (23-25 mm HgmmHg). Due to the vacuum, breast tissue is first drawn into the tray at the tip of the needle, cut by a high speed rotating blade and then suctioned into a receptacle. The number of withdrawn samples can vary from 5 to 20. With multiple rotations of the needle in one position, tissue can be sampled from a region 1-2 cm in diameter. 

All withdrawn samples are x-rayed in order to verify the presence of microcalcifications (if that was part of the target lesion).

Marking

At the end of the procedure, a radiopaque, nonmagneticnon-magnetic clip is placed through the needle into the biopsy site to identify the area on future imaging.

The needle is withdrawn, compression is applied, and the wound dressed.

Advantages

• with a single needle entry, the withdrawal of up to 20 samples (to obtain enough samples for the histological exam -at least 4-5 samples- with traditional core-biopsy the needle must be repositioned each time)
• better quality samples compared to core-biopsy (due to forced aspiration, the integrity of the samples is guaranteed and any hematic residue is eliminated
• allows any future stereotactic procedure or follow up to be easily manageable due to the titanium clip left in place
• the choice of an 11G needle makes it possible to withdraw twice the quantity of tissue compared to a 14G needle without a real increment in complications

Complications

• vasovagal reaction
• infection
• haematoma formation: uncommon