Principles of Biopsy
Aims
1. Provide representative sample
- to determine whether benign or malignant
- to determine cell line
- to grade lesion
2. Not compromise definitive treatment
Timing
Last step in evaluation / after staging
Don't perform definitive procedure immediately after biopsy unless
- pre-operative & Xray information characteristic
- fresh frozen section unquestionably confirms diagnosis
- i.e. ABC, GCT
Usually biopsy, then definitive OT later
Open vs Closed
Overall, open preferred
Open
Advantage
- more tissue
- lower sampling error
Disadvantage
- larger field to excise later
- higher local complications (i.e. infection, haematoma)
Needle Biopsy
Advantage
- less expensive / less risky
- smaller field to excise later
Disadvantage
- reduced accuracy 70-85% vs 95% with open
Indications
1. Homogenous tissue expected - Myeloma
2. Treatment unchanged by subtle differences - Soft Tissue Sarcoma
3. Diagnosis relatively certain - Metastasis
4. Access difficult - Spine, Pelvis
5. Expert histologist available
6. Patient not able to tolerate big surgery or GA
Complications biopsy tract
- wound contamination -> tumour recurrence
- wound dehiscence
- infection
- haematoma - always drain biopsies (haematoma spreads tumour)
Performed by treating surgeon at treatment centre
Results
Mankin 1982 JBJS
- complication rate x 5~12 when performed by other surgeon / other hospital
- 60% major error in diagnosis
- 20% treatment compromised by biopsy
Mankin and Simon 1996
- musculoskeletal tumour society
- follow-up study from 1982
- results no different from previous study
- 597 patients 21 institutions
- rate of diagnostic error 17.8%
- problems with biopsy causing change in treatment to more difficult or complex procedure 19.3%
- change in outcome attributed to biopsy 10.1%
- 18 patients had unnecessary amputation
- errors, complications and changes in course and outcome
- 2 - 12x more common than if biopsy done in referring institute instead of treatment centre
- 19.3% of biopsies planned poorly
Most common errors
Transverse incisions in soft tissue tumours
Needle biopsies only 60% accurate compared to 76% with open biopsy
Conclusion
Not always possible to perform biopsy in treatment centre
- do so after review of case and imaging with tumour surgeon
- discuss optimum biopsy approach
Biopsy Technique
Pre-operative
Tumour staging first / all imaging obtained
Images reviewed with experienced MSK radiologist
Treating surgeon does biopsy at treating hospital
- discussed with tumour centre if not possible
Ensure expert pathological facilities
- experienced MSK pathologist
- frozen section available
No pre-op antibiotics / infection always in DDx
Tourniquet
- no exsanguination
- release before closure and obtain hemostasis
Intra-operative
1. Approach
- plan with future OT in mind
- all aspects of biopsy tract must be excised later
- incision must be incorporated in definitive surgery
- violate one compartment only / trans-muscular
- incision is longitudinal, no undermining skin edges
- don't expose NV structures
- meticulous haemostasis
2. Biopsy
- round cortical windows / decreased stress-risers
- swab taken / tissue for M/C/S
- tissue for FFS / histology
- no closure until discussion with pathologist on phone
- ensure they have enough to make a definitive diagnosis / cell line / grade
3. Closure
- plug bone windows with PMMA / minimises tumour spread
- achieve haemostasis
- closure in layers
- drain exit site in line with and through wound
- subcuticular suture to skin
- firm dressing
- immobilise
Post operative
Very careful post op
- pathological fracture changes outcome
Team approach
- pathologist / radiologist / oncologists / radiation oncologist
- all results are reviewed to ensure correct diagnosis and management