Stereotactic Core Biopsy
Many lesions are amenable to US-guided needle biopsy
But sterotactic-guided biopsy remains important for diagnosis of
microcalcificaitons and non-palpable densities seen on mammography.
In general, breast lesions should be diagnosed by image-guided
Accuracy of stereotactic biopsy is routinely >90% in series.
Stereotactic Equipment and Principles
1. Stereotactic imaging using parallax to calculate positionos an
- ie relative shift of image with two 15o offset views
2. Most biopsies performed using a 8 - 11 guage vacuum-assisted
rotating cutting device (Mammotome-type needle)
- smaller in selected pts, e.g. those requiring anticoagulation.
- visual interpretation of stereotactic targeting to verify
4. Stroke Margin and Pullback
- ideally will position needle with target density in the middle.
- stroke is the distance it will advance when fired; stroke margin
is distance from tip of needle to image receptor.
- pullback. If the biopsy needle has a 'long throw', then if
positioned too close to the target then will target past it.
1. Review patient, indication and imaging.
- ensure stereotactic necessary and not USS-guidance adequate
2. Stop anticoagulants
- and pt must be able to lie prone for an extended period
3. Target breast with mammographic scout film; computational
calculation of positions in 3D
4. LA lignogaine; 30g then 25-22g
5. Puncture skin, then introduce device through puncture and line up
6. Prefire and postfire views necessary.
7. Take multiple biopsies (e.g. 10-15 for 11g device; 6-8 for an 8g
8. Then place a site marker, and ensure views in 2 planes.
Tips and Tricks
1. Lesions close to the chest wall
- require patient to be patient and help maneuver to turn and so on
to bring lesion close to device
- always avoid axillary structures
2. Faint lesions
- require techniques by radiography to alter view or approach to
improve the stroke margin.
- can determine course of vessels relative to tract.
If bleeding encountered, suction and continue with the biopsy; would
continue bleeding anyway.
- then suction for 5-6min.
Post-biopsy haematoma can show 4-12h later, managed with aspiration
and compression; compression dressings after biopsy can help prevent
4. Pathological Correlation
- always correlate carefully for radiological and pathological
- e.g. if lesion appears malignant, then maybe targeting was poor.
- atypical ductal and lobular hyperplasia (and radial scars) will
show a 10-20% malignancy rate after surgery even though the biopsy
Needle Biopsy Pathology that Requires
1. Any pathologic finding not corresponding to breast imaging
2. Atypical ductal hyperplasia (including atypical columnar cell
3. Atypical lobular hyperplasia
4. Radial scar (if >6mm)
5. Papillary lesions
6. Vascular proliferations (not simple hemangiomas)
7. Pseudoangiomatous stromal hyperplasia
8. When in doubt, excise (e.g. incidental lobular neoplasia)
Use in directed-therapeutics, e.g. placement of brachytherapy.