Stereotactic Biopsy

Stereotactic Core Biopsy

Intro
Key tool.
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 biopsy.
Accuracy of stereotactic biopsy is routinely >90% in series.

Stereotactic Equipment and Principles
1. Stereotactic imaging using parallax to calculate positionos an imaged target
- 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.
3. Targeting
- visual interpretation of stereotactic targeting to verify correct placement.
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.

Procedure
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 lesion
- fire
6. Prefire and postfire views necessary.
7. Take multiple biopsies (e.g. 10-15 for 11g device; 6-8 for an 8g device)
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.
3. Vessels
- 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 this.
4. Pathological Correlation
- always correlate carefully for radiological and pathological correlation
- 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 appeared accurate.

Needle Biopsy Pathology that Requires Excision
1. Any pathologic finding not corresponding to breast imaging findings (discordance)
2. Atypical ductal hyperplasia (including atypical columnar cell hyperplasia)
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)

Future Directions
Use in directed-therapeutics, e.g. placement of brachytherapy.