What is the management approach for a suspicious soft tissue mass in the thigh with irregular, multilobulated, and heterogeneously enhancing characteristics on CT scan, worrisome for a neoplastic process such as soft tissue sarcoma?

Management Approach for Suspicious Soft Tissue Mass in the Thigh

A suspicious soft tissue mass in the thigh with characteristics worrisome for a neoplastic process should be immediately referred to a specialist sarcoma multidisciplinary team (MDT) for comprehensive evaluation and management. 1

Initial Evaluation

• Any patient with an unexplained lump that is increasing in size should undergo an urgent direct access ultrasound scan within 2 weeks 1
• CT findings of an irregular, multilobulated, heterogeneously enhancing mass with intralesional calcifications strongly suggest a potential sarcoma and require prompt specialist assessment 1
• The presence of mass effect in the anterior compartment of the thigh further increases concern for malignancy and requires expedited management 1

Diagnostic Pathway

Imaging Studies

• MRI of the affected region should be performed as it provides the most accurate information for diagnosis and surgical/radiotherapy planning for extremity soft tissue tumors 1
• CT chest should be performed to exclude pulmonary metastases, as soft tissue sarcomas have a predominant pattern of metastases to the lungs 1
• Consider including abdomen and pelvis in the CT staging, especially for high-grade sarcomas of the lower extremities 1
• Regional lymph node assessment by ultrasound or cross-sectional imaging should be considered, particularly if synovial sarcoma, clear cell sarcoma, angiosarcoma, or epithelioid sarcoma is suspected 1
• PET-CT may be considered before performing radical surgery, though it is not yet proven as a routine investigation in sarcoma 1

Biopsy

• Percutaneous core needle biopsy is the standard approach to establish histopathological diagnosis 1
• Multiple cores should be taken to maximize diagnostic yield, typically performed under image guidance by a radiologist 1
• The biopsy should be planned so that the biopsy tract can be safely removed during definitive surgery 1
• Fine needle aspiration is not recommended as a primary diagnostic modality 1

Specialist Referral

• Any patient with ultrasound findings suggestive of soft tissue sarcoma should be referred via a suspected cancer pathway for an appointment within 2 weeks 1
• All patients with suspected soft tissue sarcoma should be managed by a specialist Sarcoma MDT as specified in the NICE guidance 1
• Treatment at specialized cancer centers is associated with improved survival, particularly for adolescents and young adults with soft tissue sarcomas 2

Histopathological Assessment

• Histological diagnosis should be made according to the 2020 WHO Classification of Soft tissue and bone to determine the grade and stage of the tumor 1
• A soft tissue specialist pathology review of diagnostic biopsies performed outside sarcoma centers is recommended due to high discrepancy rates (8-11% for major discordance, 16-35% for minor discordance) 1
• Tumor grade should be provided in all cases where possible based on a recognized system such as the FNCLCC grading system 1

Common Pitfalls to Avoid

• Performing "whoops surgery" (inadequate excision without proper preoperative planning) should be avoided as it often necessitates more extensive subsequent surgery 3, 4
• Relying solely on ultrasound assessment without MRI in cases of diagnostic uncertainty can lead to misdiagnosis due to the user-dependent nature of ultrasound 1
• Underestimating the extent of the tumor can result in inadequate surgical margins and increased risk of local recurrence 3, 4
• Delaying referral to specialist centers can negatively impact survival outcomes, particularly in adolescents and young adults 2

Special Considerations

• For subcutaneous soft tissue masses, careful assessment of growth speed, firmness, and mobility can provide valuable diagnostic information 3
• Masses that are deep to the fascia, are 5 cm or larger, grow rapidly, or present suddenly without explanation should prompt urgent further workup 4
• Post-radiotherapy MRI changes can sometimes mimic tumor recurrence, requiring careful interpretation in conjunction with clinical findings 5