What is the appropriate method for biopsying a mass?

How to Biopsy a Mass

Image-guided core needle biopsy is the preferred method for biopsying most masses, as it provides superior diagnostic accuracy compared to fine-needle aspiration while avoiding the complications of open surgical biopsy. 1

General Principles Across All Mass Types

Core Needle Biopsy as First-Line Approach

• Core needle biopsy is superior to fine-needle aspiration (FNA) in terms of sensitivity, specificity, and correct histological grading across breast, soft tissue, and neck masses 1
• Core biopsy allows evaluation of tumor receptor status and provides adequate tissue for molecular analysis, which FNA cannot reliably provide 1
• Multiple cores (3-4 minimum) should be obtained from representative areas under imaging guidance to maximize diagnostic yield 1, 2

Critical Technical Considerations

• The biopsy tract must be planned so it can be excised en bloc during definitive surgery if malignancy is confirmed 1, 2, 3
• The approach should be longitudinal and in line with the planned definitive surgical incision 2, 3
• Meticulous hemostasis is essential because hematoma can contaminate surrounding tissue planes with tumor cells 3
• The biopsy should avoid crossing uninvolved compartments that would not be included in definitive resection 2

Site-Specific Biopsy Approaches

Breast Masses

Ultrasound-guided core biopsy is the preferred method when the lesion is visible on ultrasound, as it offers superior patient comfort, efficiency, no radiation exposure, and real-time visualization of the needle within the lesion 1

Imaging Selection for Guidance

• If the mass is visible on both mammography and ultrasound, ultrasound guidance is preferred 1
• Stereotactic-guided biopsy is used when the target is unlikely to be seen with ultrasound (e.g., calcifications without a mass) 1
• DBT-guided biopsy may be pursued directly if the lesion is only identified on digital breast tomosynthesis 1

Post-Biopsy Protocol

• Place a marker clip with post-biopsy imaging to confirm tissue sampling and aid in correlation when biopsy guidance differs from initial detection modality 1
• This is particularly important when the finding was initially seen on mammography but biopsy was performed with ultrasound guidance 1

When FNA May Be Acceptable

• FNA may be considered only in rare situations where patient comorbidities or technical considerations (e.g., lesion abutting an implant) render core biopsy unsafe 1
• Some practices with real-time cytopathologist interpretation show good FNA results, but this is not generalizable 1

Soft Tissue Masses

Core needle biopsy using needles >16G under imaging guidance is the standard approach for suspected soft tissue sarcomas 1, 2, 4

Pre-Biopsy Imaging Requirements

• MRI with contrast is the preferred imaging modality for extremity and trunk wall masses, providing optimal information for diagnosis and surgical planning 4
• Plain radiographs should be obtained first to rule out bone tumors, detect bone erosion, and identify calcifications 4
• CT is used for retroperitoneal tumors or when MRI is not feasible 4

Biopsy Execution

• The biopsy must be performed by or in consultation with the surgeon who will perform definitive resection, or by an experienced radiologist who is part of the multidisciplinary sarcoma team 2
• Imaging guidance is necessary to avoid necrotic areas and target representative tumor tissue 2, 4
• Send samples for microbiological culture in all cases to exclude infection as a differential diagnosis 2

Special Considerations for Small Lesions

• For small subcutaneous lesions <2 cm that are indeterminate on imaging, planned excision biopsy with minimal margins may be most practical, as these usually prove benign 1
• If excision biopsy identifies a small sarcoma, further wide excision of the surgical bed is then performed 1

When to Proceed to Open Biopsy

• If core biopsy is non-diagnostic or shows only nonspecific findings despite high clinical and radiological suspicion for malignancy, proceed to open incisional biopsy rather than assuming a benign process 2
• Open biopsy should only be considered after discussion in a sarcoma specialist unit 1

Neck Masses

Fine-needle aspiration is the best initial test for diagnosing a neck mass, but core biopsy has higher sensitivity when lymphoma is suspected 1

FNA as First-Line

• FNA is well-tolerated, performed in the office setting, and has low complication rates 1
• Risks include discomfort, bruising, infection, and inadequate tissue sampling 1

When Core Biopsy is Preferred

• Core needle biopsy has higher sensitivity than FNA (92% vs 74%) when lymphoma is suspected 1
• Rapid on-site evaluation by a cytopathologist can triage tissue and direct the need for core biopsy if preliminary cytologic findings suggest lymphoma 1

Open Biopsy Indications

• Open biopsy is more invasive, requires operating room and anesthesia, and carries higher risks (anesthesia complications, infection, bleeding, scarring, nerve injury) 1
• Reserved for cases where less invasive methods fail to provide diagnosis 1

Critical Pitfall for Cystic Neck Masses

• Do not assume cystic neck masses are benign - continue evaluation until diagnosis is obtained, as cystic lymph node metastases can mimic benign branchial cleft cysts 1
• This is especially true for papillary thyroid carcinoma, lymphoma, and oropharyngeal carcinoma 1

Post-Biopsy Management

Multidisciplinary Review

• All cases must be discussed in a multidisciplinary tumor board including radiologist, pathologist, surgeon, and medical oncologist before definitive treatment planning 2
• Ensure concordance between imaging findings, clinical presentation, and pathology results 2

Follow-Up Timing

• Patients should receive biopsy results within 1 week of the procedure 1
• If results are not received after 1 week, patients should contact their provider 1

Discordance Management

• Discordance between imaging, clinical findings, and pathology mandates repeat tissue sampling 2
• Do not proceed with treatment based on discordant findings 2

Common Pitfalls to Avoid

• Never perform excisional biopsy before tissue diagnosis in a suspected sarcoma, as this compromises oncologic outcomes 2
• Do not use image-guided FNA for initial evaluation of breast masses, as it can confuse and limit image interpretation 1
• Avoid assuming all probably benign masses require immediate biopsy - short-interval follow-up is appropriate for masses with benign features on imaging in select circumstances 1
• Never place drains outside the continuity of the skin incision, as this contaminates additional tissue planes 3