Stereotactic mammotome is method of biopsing breast lesions, particularly if they are occult on ultrasound.
A vacuum assisted core biopsy (VACB)-stereotactic breast biopsy is performed as a diagnostic approach when mammography shows irregularities with micro-calcifications, parenchymal distortions, only micro-calcifications or <0.5 cm ill-defined nodules with or without micro-calcifications, all cases in which cytology can result as false-negative or provide inadequate material due to preponderance of the connective tissue.
MammotomeTM system is a VACB system that allows a certain histologic diagnosis by multiple sampling with a single entry of the needle, at low cost. It can be performed either in seated or prone position.
Patient position choice 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, patient is in front of the equipment.
A prone position is widely preferred for many reasons mainly linked to patient reactions. It is not infrequent that patients may have a vagal response in the sitting position, due to the visualization of the needle introduction into her breast, rather than from emotional tension.
A cranio-caudal projection is performed compressing the breast with a small special paddle with a central “window”.
Once the lesion is highlighted in the first mammogram, two additional projections are performed at +15 and -15 degrees. After marking the center of the lesion, it will be possible to calculate spatial coordinates X, Y and Z.
With the breast lightly compressed, the cutaneous entry point is identified. After having introduced the needle and verified the correct position of the lesion with further mammography projections, the biopsy may be performed.
MammotomeTM VACB consists of a control unit which maintains aspiration at constant values (23-25mm/Hg) and of a driver where a 11-14G needle is placed.
The system is linked to a computer where calculations are done regarding radiographic acquisitions according to stereotactic geometry principles, numerical values regulating placement and excursion of the needle to the lesion are transmitted to the driver.
The procedure is performed under local anaesthesia (1% lidocaine).
An incision of 3-4 mm is usually made by a lancet to facilitate the introduction of the needle, which can rotate 360°. Such as rotation is designed to work in an area of tissue about 1-2 cm in diameter (11G needle).
The needle tip is pushed into the lesion. The distance is controlled through an additional acquisition and corrected if necessary. Once targeting is done, system is activated. Due to the vacuum, breast tissue is first drawn to a 19 mm length window present at the tip of the needle, cut by a high speed rotating blade and then dragged onto the drawing room placed at the proximal end of the handpiece needle-holder. The number of withdrawn samples can vary from 5 to 20. The average length is 20 mm, diameter 3 mm and total weight approximately 1 gr (per 12 samples).
All withdrawn samples are placed on a radio-transparent support, according to the direction in which each sample was taken (clockwise or counterclockwise) and labeled to be x-rayed in order to verify the presence of micro-calcifications.
At the end of the procedure, a radio-opaque and non-magnetic clip is placed on site for the future recognition of the biopsied region.
The cutaneous incision is dressed with a steri-strip tape and a compressive bandage is applied for 24 hours. A pack of instant ice is also applied.
- MammotomeTM VACB allows, 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)
- MammotomeTM VACB allows a better quality samples withdrawal compared to core-biopsy (due to forced aspiration, the integrity of the samples is guaranteed and any hematic residue is eliminated
- MammotomeTM VACB allows any future stereotactic procedure or follow up to be easily manageable due to the titanium clip left in place
- the choice of a 11G needle makes it possible to withdraw twice the quantity of tissue compared to a 14G needle without a real increment in complications
Equipment, disposable consumables and needles are very expensive, but in terms of cost evaluation, the VACB should not be compared to FNAB, as the choice between both methods is not arbitrary but indicates a strict selection of the cases to expose to one or the other technique. This correct behaviour makes the MammotomeTM VACB less expensive than a surgical biopsy or repetitive follow-up.
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