What type of biopsy is recommended for sarcoma diagnosis?

Recommended Biopsy Type for Sarcoma Diagnosis

Multiple core needle biopsies are the standard approach for diagnosing sarcomas, with excisional biopsy being appropriate only for small (<5 cm) superficial lesions. 1

Primary Diagnostic Approach

• Core needle biopsy (CNB) is the recommended first-line approach for diagnosing soft tissue or visceral lesions >3 cm 1
• Multiple cores should be taken to maximize diagnostic yield, typically 4-6 cores varying the angle into the tumor 1
• The biopsy should be performed under imaging guidance (usually ultrasound or CT) to avoid areas of necrosis 1
• Use of G14 or G16 needles with a coaxial introducer for a single skin entrance is recommended 1

Special Considerations

• The biopsy should be planned so that the biopsy tract can be safely removed during definitive surgery 1
• The procedure should be performed by a trained surgeon or discussed between the surgeon and radiologist 1
• Imaging (preferably contrast-enhanced MRI for limb and superficial trunk lesions) should precede the biopsy 1
• The risk of tumor seeding in the biopsy tract is very small but should still be considered in planning 1

Alternative Biopsy Options

• Excisional biopsy may be the most practical option for small (<5 cm) superficial lesions 1
• Planned excision biopsy with minimal margins may be appropriate for small subcutaneous lesions (<2 cm) that are indeterminate on imaging, as these usually prove benign 1
• Open incisional biopsy should only be considered in exceptional circumstances when adequate tissue cannot be obtained by core needle biopsy, and only after discussion in a sarcoma specialist unit 1
• Fine needle aspiration is not recommended as a primary diagnostic modality, although it may be used for confirming disease recurrence or nodal metastases 1

Diagnostic Accuracy

• Core needle biopsy has high accuracy rates when performed and reviewed by experienced specialists 2, 3
• Studies show 87-95% accuracy for determining malignancy 3, 4, 5
• 80-92% accuracy for identifying histologic subtype 3, 6
• 84-87% accuracy for determining tumor grade 3, 5

Advantages of Core Needle Biopsy

• Minimal morbidity compared to open biopsy 4, 5
• Faster time to diagnosis and treatment recommendation 3
• Lower cost and resource utilization 5
• Allows for one-surgery planning or neoadjuvant therapy when combined with appropriate imaging 5

Pathological Assessment

• Histological diagnosis should be made according to the WHO classification 1
• Grading should be based on the FNCLCC system, which distinguishes three malignancy grades 1
• Core biopsies may underestimate tumor grade due to tumor heterogeneity and underrepresentation of necrosis 1
• Molecular pathology (FISH, RT-PCR) should complement morphology and immunohistochemistry, particularly when the clinical-pathologic presentation is unusual 1

Caution and Pitfalls

• A core biopsy may underestimate tumor grade compared to final pathology due to tumor heterogeneity 1
• Central pathological review by an expert sarcoma pathologist is strongly recommended due to high discrepancy rates (8-11% for major discordance, 16-35% for minor discordance) 1
• If core needle biopsy yields inadequate tissue, open biopsy should be considered 4
• Tumor samples should be fixed in formalin (avoid Bouin fixation as it may impair molecular analysis) 1