Principles of Biopsy

Definition

Golden Rule

• Bailey and Love's Short Practice of Surgery, 28th Ed.

Types of Biopsy

1. Fine-Needle Aspiration Cytology (FNAC)

• Uses a thin (21-23 G) needle to aspirate cells (not tissue cores)
• Provides cytological, not histological, diagnosis
• Advantages: Cost-effective, fewer complications, good for superficial or deep-seated lesions (US/CT-guided), excellent for metastases, lymph nodes, thyroid
• Disadvantages: Small sample, no tissue architecture, needs an expert cytopathologist; accuracy for specific tumor type is lower (~90% for malignancy vs. ~70% for specific histological type)
• Campbell's Operative Orthopaedics, 15th Ed.

2. Core Needle Biopsy (Tru-Cut / Jamshidi)

• Larger-gauge needle preserving tissue architecture
• Provides histological diagnosis + immunohistochemistry, receptor status, molecular markers
• Diagnostic accuracy: 84-98% overall; 97% for malignancy/benignity; 81% for specific histopathologic diagnosis and grade
• Jamshidi needles preferred for bone tumours; Tru-Cut needles for soft-tissue tumours
• Image guidance (USS or CT) improves yield and safety; image-guided biopsy is now standard of care
• Bailey and Love's; Campbell's Operative Orthopaedics

3. Incisional Biopsy

• A portion of the lesion is surgically excised for diagnosis
• Indicated when the lesion is >3 cm, needle biopsy is non-diagnostic, or more tissue is required for cytogenetics/flow cytometry
• More tissue available but carries higher risk of bleeding, infection, and tumour contamination
• Must follow strict oncological principles (see below)

4. Excisional Biopsy

• Complete removal of the entire lesion - simultaneously diagnostic and therapeutic
• Preferred for small lesions (<3 cm), polyps, and lymph nodes
• For polyps: partial biopsy should be avoided - the pathologist needs to assess invasion through the muscularis mucosae (the criterion of malignancy); complete excision biopsy is preferred
• Pye's Surgical Handicraft, 22nd Ed.

Principles of Open/Incisional Biopsy

1. Staging Before Biopsy

• Complete all local and systemic staging (MRI, CT, bone scan, PET) before the biopsy is performed
• Biopsy should be performed at, or after discussion with, a specialist tumour centre
• Bailey and Love's, 28th Ed.

2. Longitudinal Incision

• The skin incision must be longitudinal, in line with the extremity and the planned definitive resection
• A longitudinal incision is extensile and allows the entire biopsy tract to be excised en bloc at definitive surgery
• Transverse incisions contaminate a wide field and may render limb salvage impossible
• Miller's Review of Orthopaedics, 9th Ed.; Rockwood & Green's Fractures, 10th Ed.

3. Single-Compartment Access

• The biopsy must be performed through a single compartment
• Do not cross anatomical compartments - crossing compartments spreads tumour to uninvolved tissue planes and can convert a resectable lesion into one requiring amputation

4. Avoid Critical Structures

• The biopsy tract must avoid major nerves, blood vessels, and joints
• Contamination of a neurovascular bundle may render limb salvage impossible
• Miller's Review of Orthopaedics

5. Biopsy Tract Excision

• The biopsy track is regarded as contaminated by tumour cells
• It must be excised en bloc with the tumour at definitive surgery
• If a drain is placed, it must exit in line with the incision so the drain track can also be excised
• Bailey and Love's; Campbell's Operative Orthopaedics

6. Meticulous Haemostasis

• A tourniquet may be used to improve visibility, but exsanguination by compression wrapping (e.g., Esmarch bandage) should be avoided - this may mechanically disseminate tumour cells into the circulation
• Tourniquet must be deflated and haemostasis secured before wound closure
• Postbiopsy haematoma is considered tumour-contaminated; all tissue soaked by haematoma must be excised at definitive surgery
• Bailey and Love's; Campbell's Operative Orthopaedics

7. Handling Bone Defects

• If a cortical window is made in bone, it should be round or oval (not rectangular) to minimise stress concentration and reduce the risk of pathological fracture
• The defect should be plugged with bone cement (polymethylmethacrylate) to limit haematoma formation - but excessive cement must be avoided as it can push tumour along the medullary canal

8. Send for Microbiology As Well As Histopathology

• Cultures must always be sent alongside histopathology samples - infection can closely mimic tumour radiographically ("biopsy every infection, culture every tumour")
• Some specimens require fresh tissue for genetic studies (cytogenetics, flow cytometry)
• Rockwood & Green's; Miller's Review of Orthopaedics

9. Representative Sampling

• For carcinomas, the biopsy should be taken from the edge of the lesion (viable tumour margin) using large cup forceps - the centre may be necrotic and non-diagnostic
• Soft tissue component of a bone tumour is preferred over pure cortical/bone sampling - this avoids creating a stress riser and pathological fracture
• Pye's Surgical Handicraft; Miller's Review of Orthopaedics

10. Wound Closure

• Wound should be closed in tight layers
• Wide retention sutures should not be used as they broaden the contamination field that would need to be excised later

Contraindications and Special Precautions

• Biopsy is contraindicated in patients on anticoagulants or with clotting disorders (significant bleeding risk)
• After a rectal biopsy, a barium enema must not be performed within 10 days due to risk of perforation at the biopsy site
• After biopsy, the site must be inspected for bleeding; local adrenaline (1:1000) can be used to achieve haemostasis endoscopically
• Pye's Surgical Handicraft

Summary Table: Types of Biopsy