Biopsy and Drainage · IR Playbook

Image-Guided Soft-Tissue, Lymph-Node and Deep Pelvic or Retroperitoneal Biopsy

Image-guided percutaneous needle biopsy obtains cells or tissue from soft-tissue masses, lymph nodes and deep pelvic or retroperitoneal lesions for histology, immunophenotyping, microbiology or molecular testing. Core needle biopsy is preferred for most tumors and lymph nodes because it preserves architecture, while fine-needle aspiration is principally an adjunct for cytology or flow cytometry. Superficial compressible biopsies have low bleeding risk, whereas deep pelvic and retroperitoneal biopsies are high-risk procedures requiring meticulous trajectory planning and haemostatic preparation.

Learning objectives

• Select US or CT guidance according to target visibility, depth and the safety of the access window.
• Plan a biopsy tract that avoids critical structures and does not compromise future sarcoma surgery.
• Choose between core biopsy, FNA and excisional biopsy according to the diagnostic question.
• Allocate specimens correctly for histology, flow cytometry, molecular testing and microbiology.
• Recognize and manage bleeding, visceral injury, infection and neural injury promptly.

Indications

• Differentiate benign, malignant, inflammatory and infectious soft-tissue or nodal disease.
• Establish the histologic type, grade, immunophenotype or molecular profile of a suspected malignancy.
• Confirm nodal or soft-tissue metastasis for staging or suspected recurrence.
• Obtain tissue from an inaccessible deep pelvic or retroperitoneal lesion when a safer superficial target is unavailable.
• Obtain material for microbiological examination when infection is suspected and aspiration alone is insufficient.
• Re-biopsy a known malignancy when contemporary tissue is required for biomarker-directed therapy or a clinical trial.

Absolute contraindications

• Patient refusal or absence of valid consent.
• No safe percutaneous access route.
• Non-correctable coagulopathy for the planned depth and bleeding-risk category.

Relative contraindications

• Inability to cooperate or remain in the required position.
• Haemodynamic or respiratory instability.
• Pregnancy when CT or another ionizing-radiation technique is required.
• Hypervascular target, severe thrombocytopenia or ongoing antithrombotic effect.
• Suspected resectable sarcoma without multidisciplinary biopsy-tract planning.
• Suspected lymphoma when an accessible node can be safely excised and architectural assessment is essential.

Equipment

• High-frequency linear US transducer for superficial targets and low-frequency curvilinear transducer for deeper targets, with sterile cover and sterile gel
• Multidetector CT or CT-fluoroscopy with radiopaque skin grid and dose-reduction capability
• 17–19G coaxial introducer compatible with the selected biopsy device
• 18G automated or semi-automated core biopsy needle with a selectable throw appropriate to lesion thickness
• 14–16G core device when required by an agreed sarcoma protocol and safe tract
• 18–25G Chiba, spinal or dedicated aspiration needle with 10–30 mL syringe for FNA
• 1–2% lidocaine, 10–20 mL syringe and 22–25G infiltration needle
• Sterile preparation set, drapes, scalpel, gauze and compression dressing
• 10% neutral-buffered formalin containers, sterile microbiology container and laboratory-specified fresh transport medium for flow cytometry
• Slides and cytology fixatives when FNA, touch preparations or rapid on-site evaluation are planned
• Sterile saline, connecting tubing and needles for hydrodissection when required
• Gelfoam pledgets or slurry for selective coaxial tract embolization in an anticipated high-bleeding-risk tract

Procedure steps

1. Verify the target, diagnostic question, bleeding-risk category and required specimen tests. Confirm that sarcoma tract planning, lymphoma architecture requirements and microbiology or molecular requests have been addressed before opening the biopsy device.Pearl: The procedure succeeds only when the obtained tissue is suitable for the test that will change management.
2. Position the patient to create the safest and most stable window. Perform a limited US or CT survey, mark the entry point and measure the skin-to-target distance, trajectory angle and safe biopsy throw.Pearl: Small changes in prone, oblique or decubitus positioning may move bowel or vessels away from the tract.
3. Use Doppler, contrast-enhanced imaging or multiplanar CT reformations when necessary. Confirm safety along the complete path of both the introducer and the deployed cutting cannula.
4. Perform wide sterile preparation and draping. Infiltrate the skin, subcutaneous tissues and deeper muscular tract with 10–20 mL of 1–2% lidocaine while remaining within the safe weight-based dose; make a small skin nick for the coaxial introducer.
5. If bowel or another mobile structure obstructs the tract, reposition the patient or perform controlled sterile saline hydrodissection under imaging. Re-image to confirm that displacement remains adequate before advancing the biopsy needle.
6. Advance the coaxial introducer incrementally under continuous US visualization or serial limited CT acquisitions. Stop at the near margin of the target, remove the stylet and occlude the hub whenever the lumen is open.Pearl: The coaxial technique permits multiple samples through one organ or muscle puncture and facilitates tract embolization when required.
7. Confirm the planned throw within viable tissue and fire the core device only when the entire excursion is safe. Obtain multiple intact cores from representative regions according to the pathology plan, redirecting through the coaxial cannula when lesion heterogeneity requires sampling of more than one viable area.Pearl: For suspected lymphoma, maximize usable core tissue and conserve material for immunohistochemistry, flow cytometry and molecular studies.
8. Perform FNA through the same coaxial access when cytology, rapid on-site assessment or a fresh cellular sample is required. Release suction before withdrawing the aspiration needle to limit contamination from the needle tract.
9. Place routine histology cores in formalin. Send designated lymphoma material fresh in the laboratory-specified medium and suspected infection material unfixed in a sterile microbiology container; label every container with the target and requested examination.Pearl: Agree the allocation before biopsy because transport requirements vary between laboratories.
10. Remove the introducer while applying manual compression; selectively plug a high-risk tract when planned. Perform an immediate US or limited CT survey for haemorrhage, pneumothorax, free gas or adjacent-organ injury and document the biopsy site, needle sizes, passes, specimens and complications.

Complications

• Local pain, bruising or vasovagal reaction
• Haemorrhage or expanding haematoma
• Bowel, urinary tract or other adjacent-organ injury
• Neural injury
• Biopsy-site infection or abscess
• Needle-tract tumor seeding or sarcoma-compartment contamination

Exam pearls

• Tissue adequacy, not merely needle placement, defines technical success.
• Use US when the target and entire needle path are visible; use CT for deep, complex or bone-obscured trajectories.
• A superficial compressible node is low bleeding risk, but a deep pelvic or retroperitoneal node is high risk.
• For suspected lymphoma, core tissue must be conserved and correctly divided; formalin destroys material required for flow cytometry.
• For suspected sarcoma, perform MRI and tumor-center review before biopsy and place the tract within the future resection field.
• Always assess the complete automated needle throw because the cutting cannula may extend beyond an apparently safe needle-tip position.

Viva questions

Why is core biopsy preferred over FNA for most lymph nodes and soft-tissue tumors?

Core biopsy preserves tissue architecture and provides material for histology, immunohistochemistry and molecular testing. FNA supplies cells but may not reliably classify lymphoma or grade a heterogeneous soft-tissue tumor.

When should excisional biopsy be preferred for suspected lymphoma?

Excisional biopsy is preferred when a node is surgically accessible and architectural assessment is required. Image-guided core biopsy is appropriate for deep or surgically hazardous nodes, but an inadequate core biopsy should generally prompt excision rather than repeated small-volume sampling when excision is feasible.

How do superficial and deep lymph-node biopsies differ in bleeding-risk classification?

A superficial compressible node is low risk and often does not require routine coagulation screening or interruption of antithrombotic therapy. Retroperitoneal, mediastinal and deep pelvic nodes are high risk because haemorrhage is difficult to compress or detect clinically.

What is the key rule when biopsying a suspected soft-tissue sarcoma?

Refer or discuss the patient with the specialist tumor team before biopsy. The tract should remain within one compartment, avoid neurovascular structures and be positioned so it can be removed during definitive surgery.

What are the principal CT-guided approaches to a deep pelvic lesion?

The main approaches are anterior transabdominal, transgluteal and anterolateral through the iliopsoas. A transsacral or transiliac route is reserved for lesions without a safe soft-tissue window.

How should tissue be divided when lymphoma is suspected?

Allocate intact cores for formalin-fixed histology and immunohistochemistry while sending designated fresh tissue in the laboratory-specified medium for flow cytometry and other studies. The exact allocation must be agreed with hematopathology before biopsy.

What defines technical success of percutaneous needle biopsy?

Technical success is procurement of sufficient representative material to establish the diagnosis or guide treatment. Needle placement in the lesion without diagnostically usable tissue is not a successful biopsy.

What should you do if active bleeding is seen before removing the coaxial introducer?

Leave controlled access in place while assessing severity because the cannula may provide tamponade or permit tract embolization. Resuscitate, reverse anticoagulation when appropriate and proceed to angiographic embolization for ongoing arterial bleeding.

References