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