NCCN Guidelines for Soft Tissue Sarcoma Diagnosis
The diagnosis of soft tissue sarcoma requires evaluation by a multidisciplinary team with demonstrated expertise in sarcoma management, including thorough imaging studies, appropriate biopsy techniques, and expert pathologic assessment with molecular testing when indicated. 1
Initial Evaluation and Workup
History and Physical Examination
- Assess for risk factors:
- Prior radiation therapy to the affected area
- Chemical exposures (e.g., herbicides such as Agent Orange)
- Genetic syndromes (e.g., Li-Fraumeni syndrome, neurofibromatosis) 1
Imaging Studies
- For suspected STS:
- CT is the preferred imaging modality for retroperitoneal/intra-abdominal STS
- MRI may be used in certain situations
- Chest imaging is required for histologies with potential for lung metastases 1
Biopsy Principles
- Pretreatment biopsy is highly preferred for diagnosis and grading of STS 1
- Core needle biopsy is the preferred technique and should be performed by an experienced surgeon or radiologist 1
- Open incisional biopsy may be considered by an experienced surgeon when necessary
- Fine-needle aspiration (FNA) alone is discouraged due to limited specimen size 1
- For deep thoracic, abdominal, or pelvic STS, endoscopic or needle biopsy may be indicated
- For retroperitoneal STS:
- Preresection biopsy is not necessary for all patients
- Image-guided core needle biopsy is preferred if neoadjuvant therapy is being considered or if there's suspicion of malignancy other than sarcoma 1
Pathologic Assessment
Essential Components of Pathology Report
- Primary diagnosis using standardized WHO Classification of Soft Tissue Tumors
- Organ and site of sarcoma
- Depth and size of tumor
- Histologic grade
- Presence or absence of necrosis
- Status of excision margins and lymph nodes
- TNM stage
- Additional features:
- Mitotic rate
- Presence/absence of vascular invasion
- Type and extent of inflammatory infiltration 1
Ancillary Diagnostic Techniques
- Morphologic assessment based on microscopic examination remains the gold standard
- Supplementary techniques include:
- Conventional cytogenetics
- Immunohistochemistry (IHC)
- Electron microscopy
- Molecular genetic testing 1
Molecular Diagnosis
- Particularly useful for STS subtypes with characteristic genetic aberrations
- STS can be divided into two major genetic groups:
- Sarcomas with specific genetic alterations (chromosomal translocations or point mutations) and simple karyotypes
- Sarcomas with nonspecific genetic alterations and complex unbalanced karyotypes 1
- Specific molecular testing:
- SDH gene mutational analysis for GIST lacking KIT or PDGFRA mutations
- Loss of SDHB protein expression by IHC can screen for patients appropriate for germline mutation testing
- Family history evaluation for FAP or Gardner syndrome in patients with desmoid tumors 1
Diagnostic Challenges and Pitfalls
Common pitfalls:
- Misdiagnosis of STS as benign lesions
- Inadequate biopsy sampling leading to underestimation of grade
- Inappropriate biopsy techniques compromising definitive surgical management
- Failure to recognize the need for expert pathologic review
To avoid these pitfalls:
- Refer patients with suspected STS to diagnostic centers with sarcoma expertise
- Ensure pathologists with expertise in STS review biopsies and resected specimens
- Use appropriate ancillary diagnostic techniques when necessary
- Consider repeat image-guided core needle biopsy if initial biopsy is inconclusive 1
Disease-Specific Considerations
The NCCN Guidelines address management of STS in adult patients from the perspective of the following disease subtypes:
- STS of extremity, superficial/trunk, or head and neck
- Retroperitoneal or intra-abdominal STS
- Desmoid tumors (aggressive fibromatoses)
- Rhabdomyosarcoma 1
Each subtype requires specific diagnostic considerations based on anatomic location and clinical presentation.