What is the most appropriate method to confirm the diagnosis of sarcoma in a patient with a soft tissue mass?

Core Biopsy is the Most Appropriate Method to Confirm Sarcoma Diagnosis

The most appropriate method to confirm the diagnosis of sarcoma in a patient with a soft tissue mass is core needle biopsy (b). 1, 2

Rationale for Core Needle Biopsy

Core needle biopsy (CNB) represents the optimal diagnostic approach for several key reasons:

• It provides the optimal balance between diagnostic accuracy and minimal patient morbidity, with high sensitivity (97%) and specificity (99%) for determining malignancy 2
• It is specifically recommended as the standard approach by current guidelines for establishing a histopathological diagnosis of suspicious soft tissue masses 1
• It allows for adequate tissue sampling for complete histological assessment, grading, and molecular testing 2

Comparison with Alternative Methods

Fine-Needle Aspiration (FNA)

• Not recommended as a primary diagnostic modality for suspected sarcomas 1
• Insufficient tissue sampling for complete diagnosis, especially when preoperative treatment is planned 2
• May be considered only for confirming disease recurrence or nodal metastases, not primary diagnosis 1

Incisional Biopsy

• Should only be considered in exceptional circumstances when core biopsy cannot provide adequate tissue 1
• Requires discussion in a sarcoma specialist unit before proceeding 1
• Causes unnecessary contamination of tissue compartments compared to CNB 2

Local Excision/Enucleation

• Contraindicated for potentially malignant lesions of this size (8 × 4 cm) 2
• Should only be considered for small (<2 cm) subcutaneous lesions that are indeterminate on imaging 1
• Risks inadequate margins and tumor spillage, compromising definitive treatment 1

Proper Core Biopsy Technique

For optimal diagnostic results:

• Use needles ≥16G to ensure adequate tissue sampling 2
• Take multiple cores to maximize diagnostic yield 1
• Plan the biopsy tract so it can be safely removed during definitive surgery 1, 2
• Have samples evaluated by pathologists with expertise in musculoskeletal tumors 2

Diagnostic Accuracy of Core Needle Biopsy

When properly performed, core needle biopsy provides:

• 95% accuracy for determining malignancy 3
• 88% accuracy for determining histologic grade 3
• 75% accuracy for determining histologic subtype 3
• 93% specimen adequacy rate 3

Important Considerations

• The biopsy should be planned so the tract can be removed during definitive surgery 1, 2
• Fresh tissue may be collected for whole genome sequencing if sarcoma is confirmed 1
• Histological diagnosis should follow the WHO Classification with grading using the FNCLCC system 1, 2
• A specialist sarcoma pathologist should review the biopsy to minimize diagnostic discrepancies 1

For this 45-year-old man with an 8 × 4 cm soft tissue mass in the right thigh, core needle biopsy represents the most appropriate initial diagnostic approach to confirm sarcoma while minimizing morbidity and preserving treatment options.