What is the diagnostic approach for a patient presenting with suspected soft tissue sarcoma?

Diagnostic Approach for Suspected Soft Tissue Sarcoma

All patients with suspected soft tissue sarcoma must be referred immediately to a specialized sarcoma multidisciplinary tumor board before any definitive intervention, as management at reference centers significantly improves clinical outcomes and cost-effectiveness. 1

Initial Clinical Recognition and Referral Triggers

Refer urgently (within 2 weeks) any patient presenting with: 1

• Any unexplained deep soft tissue mass of any size
• Superficial lesions >5 cm in diameter
• Any soft tissue mass in pediatric patients
• Lesions increasing in size (pain presence or absence does not predict malignancy) 2, 3

Imaging Strategy

Primary Local Imaging

MRI with contrast is the mandatory first-line imaging modality for extremity, trunk wall, and pelvic lesions. 1

• Provides optimal detail for surgical planning and helps estimate malignancy grade by detecting necrosis 1
• Standard radiographs should be obtained initially only to rule out bone tumors, detect bone erosion/fracture risk, and show calcifications 1

CT scan is the preferred imaging for: 1

• Retroperitoneal tumors (performance equivalent to MRI)
• Thoracic, abdominal, and head/neck lesions 2, 4
• Calcified lesions to exclude myositis ossificans 1

Staging Imaging (Mandatory Before Treatment)

Chest CT scan is required in all cases to detect pulmonary metastases. 1, 5

Additional staging imaging based on histologic subtype: 1

• Abdominal/pelvic CT for myxoid liposarcoma, epithelioid sarcoma, angiosarcoma, leiomyosarcoma, and small-cell sarcomas (high metastatic potential)
• Spine and pelvic MRI for myxoid liposarcoma specifically
• Baseline brain MRI for alveolar soft-part sarcoma, angiosarcoma, and clear cell sarcoma (high CNS metastasis risk)

Tissue Diagnosis Protocol

Biopsy Technique

Core needle biopsy using 14-16G needles is the standard diagnostic approach for lesions >3 cm. 1

Critical technical requirements: 1

• Image guidance mandatory to avoid necrotic areas
• Coaxial introducer for single skin entrance
• Obtain 4-6 cores varying the angle into the tumor
• Biopsy must be planned by the multidisciplinary team so the tract can be excised during definitive surgery 1
• Consider tattooing the entrance point 1

Alternative biopsy approaches: 1

• Excisional biopsy is acceptable for superficial lesions <5 cm
• Open biopsy may be used in selected cases after interdisciplinary discussion
• Fine needle aspiration is NOT recommended except at institutions with specific expertise 1
• Frozen section for immediate diagnosis is NOT encouraged as it prevents complete diagnosis, especially when neoadjuvant treatment is planned 1

Pathology Requirements

Histological diagnosis must follow the most recent WHO classification with FNCLCC grading system. 1

Central pathological review by an expert sarcoma pathologist is strongly recommended. 1

Molecular pathology testing is required when: 1

• Morphology and immunohistochemistry are insufficient for precise diagnosis
• Additional prognostic/predictive information is needed

Critical caveat: Core biopsy may underestimate tumor grade, so radiological imaging (particularly evidence of necrosis) should supplement pathology in estimating malignancy grade when neoadjuvant treatment is considered. 1

Multidisciplinary Tumor Board Requirements

All diagnostic procedures and therapeutic decisions must be discussed within a weekly multidisciplinary tumor board that includes: 1

• Medical oncology
• Radiology
• Surgery
• Pathology
• Radiation oncology
• Pediatrics (if applicable)

The multidisciplinary team should be defined by: 1

• Weekly meeting periodicity
• Contribution to clinical trials and scientific production
• Participation in national/international guidelines
• Periodic quality audits

Common Pitfalls to Avoid

Never perform definitive surgical resection before multidisciplinary evaluation and proper imaging. 1

Do not perform biopsy without planning the tract for subsequent excision during definitive surgery. 1

Avoid using Bouin fixation for tissue samples as it prevents molecular analysis; use 4% buffered formalin instead. 1

Do not rely solely on core biopsy grade determination—integrate radiological findings (especially necrosis) when planning neoadjuvant therapy. 1