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  • Summary
    • Soft tissue sarcomas are rare, malignant tumors comprising of a variety of subtypes distinguished by histological findings. 
    • The condition usually presents in patients > 15 years old with a slow-growing, painless soft tissue mass.
    • Diagnosis is made by biopsy and histological findings. 
    • Treatment usually involves mass excision and radiation therapy.
  • Epidemiology
    • Incidence
      • 12,000 new cases/year in the United States
        • 4,700 deaths/year in the United States
    • Demographics
      • males > females
      • 85% occur in patients >15 years old
    • Anatomic location
      • 60% occur in extremities
      • 44% occur in the thigh
  • Etiology
    • Genetics
      • classic translocations
        • t(X;18); SYT-SSX fusion
          • synovial sarcoma
        • t(2:13)
          • rhabdomyosarcoma (alveolar)
        • t(12;16)(q13:p11)
          • myxoid liposarcoma
    • Associated conditions
      • neurofibromatosis type-1
        • malignant peripheral nerve sheath tumor (MPNST)
      • Stuart-Treves syndrome
        • angiosarcoma
      • chronic lymphedema
        • angiosarcoma
  • Classification
    • Classification of STS is based on histology, with over 50 types recognized
      • all STS have the same presentation, imaging, differential diagnosis, and treatment
      • histologic findings and molecular signatures are used to distinguish individual types
      • commonly tested soft tissue sarcomas include
        • undifferentiated pleomorphic sarcoma (UPS; previously malignant fibrous histiocytoma)
        • malignant peripheral nerve sheath tumor (MPNST)
        • synovial sarcoma
        • liposarcoma
        • rhabdomyosarcoma
        • fibrosarcoma
        • leiomyosarcoma
        • epithelioid sarcoma
        • angiosarcoma
        • dermatofibrosarcoma protuberans
        • clear cell sarcoma
        • alveolar soft part sarcoma (ASPS)
      • soft tissue sarcomas that metastasize to lymph nodes (when it RACES to the lymph nodes)
        • Rhabdomyosarcoma, Angiosarcoma, Clear cell sarcoma, Epithelioid sarcoma, Synovial sarcoma
        • Overall, only 5% of soft tissue sarcomas metastasize to lymph nodes
    • AJCC staging system is used for interdisciplinary communication
      • AJCC Staging System for Soft Tissue Sarcoma of the Extremity or Trunk
      • Stage
      • Size
      • Lymph Node Involvement
      • Metastasis
      • Grade
      • IA
      • < 5 cm
      • None/unknown
      • None
      • Low
      • IB
      • > 5 cm
      • None/unknown
      • None
      • Low
      • II
      • < 5 cm
      • None/unknown
      • None
      • Intermediate/high
      • IIIA
      • 5-10 cm
      • None/unknown
      • None
      • Intermediate/high
      • IIIB
      • > 10 cm
      • None/unknown
      • None
      • Intermediate/high
      • IV
      • Any
      • Any
      • Any
      • Any
  • Presentation
    • History
      • may have a history of trauma that draws attention to the mass
    • Symptoms
      • slow growing, painless mass
        • incidental trauma often draws attention to mass
        • rapid growth usually suggests a higher grade
    • Physical exam
      • inspection
        • mass may be palpable
        • lack of ecchymosis suggests an encapsulated mass
          • could contradict diagnosis of hematoma, which typically presents with ecchymosis after trauma
      • palpable soft tissue lesion
        • differentiating whether a mass is above or below fascia has prognostic importance
        • poor prognostic indicators include >5cm, deep to fascia, and immobile
      • can be confused with more common pathology
        • lipoma
        • hematoma
        • desmoid tumor
        • nerve sheath tumors
      • assess local lymph nodes
  • Imaging
    • Radiographs
      • indications
        • obtain plain radiographs in at least two planes for initial workup
      • findings
        • may show soft tissue shadow or mineralization (most commonly with synovial sarcoma)
    • CT chest
      • indications
        • obtain to assess for metastatic disease
        • an exception is that a CT chest/abdomen/pelvis is indicated for myxoid liposarcoma
    • MRI with contrast
      • indications
        • mandatory to evaluate soft tissue lesions in the extremities and determine treatment algorithm
      • findings
        • T1: low signal intensity (isointense with muscle)
        • T2: high signal intensity
        • IV gadolinium: peripheral enhancing zone and non-enhancing necrotic center
      • can be diagnostic for the following benign lesions
        • if MRI is diagnostic and the mass is benign and symptomatic, then it can be removed without a biopsy
        • lipoma
        • ganglion cyst
        • neurilemoma (schwannoma)
        • intramuscular myxoma
      • indeterminate MRI
        • if MRI is indeterminate or suggestive of sarcoma, then a core needle or open biopsy must be obtained before further treatment is initiated
        • be cautious of a "hematoma" without associated trauma because they can have similar appearances
    • PET
      • evolving indications
      • particularly useful for sarcomas that metastasize to lymph nodes
  • Studies
    • Histology
      • determined by type of sarcoma
        • undifferentiated pleomorphic sarcoma
        • malignant peripheral nerve sheath tumor
        • synovial sarcoma
        • liposarcoma
        • rhabdomyosarcoma
        • fibrosarcoma
        • leiomyosarcoma
        • epithelioid sarcoma
        • angiosarcoma
        • dermatofibrosarcoma protuberans
  • Differential
    • Differentiate from benign soft tissue masses with MRI and biopsy
      • Hematoma
      • Lipoma
      • Intramuscular Myxoma
      • Hemangioma of Soft Tissue
      • Calcifying Aponeurotic Fibroma
      • Plantar Fibromatosis (Ledderhose Disease)
      • Extra-abdominal Desmoid Tumor
      • Nodular Fasciitis
      • Neurofibroma
      • Neurilemmoma
      • Neuroma
  • Treatment
    • Operative
      • biopsy
        • indications
          • mass concerning for malignancy after clinical and radiological workup
        • outcomes
          • core needle biopsy (modality of choice) identifies the correct diagnosis in 68-93% of cases
          • best results if done at the institution where definitive surgery will take place, under a multidisciplinary team
          • 2-12 times more complications when biopsy is not performed by the treating team
      • wide surgical resection & radiation therapy
        • indications
          • standard of care in most cases
            • except synovial sarcoma which is treated with chemotherapy
          • treatment must be based on a tissue diagnosis unless images are diagnostic (i.e. lipoma)
          • tumors that surround/encase critical structures require the removal with the tumor en-bloc
          • tumors adjacent to/abutting critical structures can be removed with close or microscopically positive margins along critical structures without significant impact on oncologic outcomes (i.e. local recurrence)
          • radiation is an important adjunct to surgery decreasing local recurrence, regardless of the marginal status after resection (i.e. adjuvant radiation is important even when the tumor was removed with negative margins)
          • chemotherapy is controversial for soft tissue sarcomas
            • randomized controlled trials have not shown a survival benefit for most soft tissue sarcomas
            • consider in high-grade tumors that have a higher risk of distant metastases
            • considered standard of care for rhabdomyosarcoma and Ewing sarcoma
        • outcomes
          • reduces risk of local recurrence to less than 10% for low-grade disease
      • amputation
        • indications
          • when otherwise unable to resect tumor with negative margins
            • most frequently in the foot
          • resection would result in irreversible damage to major nerves
          • patient comorbidities limit potential for recovery after limb-sparing surgery
        • outcomes
          • good prognosis in absence of metastatic disease
      • surgical resection of lung metastases
        • indications
          • first-line for pulmonary metastases if the preop evaluation shows that complete resection is possible
        • outcomes
          • curative in up to 25% of patients
  • Techniques
    • Biopsy
      • approach
        • longitudinal incision
          • transverse incisions are contraindicated due to a need for wider resection at time of surgery
      • technique
        • use anatomic route that limits contamination of compartments and neurovascular structures
        • maintain meticulous hemostasis
        • use knife or curette to remove tissue
        • drains should be placed distal and in line with the surgical incision to allow removal of drain site with extensile incision
        • requires a specialized pathologist to interpret the results accurately
    • Wide resection & radiation therapy
      • approach
        • elliptical incision used to incorporate biopsy and drain sites
      • technique
        • resection
          • use of tourniquet without exsanguination
          • maintain meticulous hemostasis
          • meticulous dissection to ensure wide margins must confirm border free of disease with histology
            • frozen section can be used to ensure margins are free of tumor
        • consideration of nearby neurovascular and bony structures
          • resection of neurovascular structures may be performed if bypass grafting is possible
          • resection should only be performed if the resulting morbidity is acceptable to the patient
          • current evidence suggests little difference in local recurrence between planned positive margins with the adventitia/perineurium removed versus negative margins
          • resection of >10cm periosteum increases risk of fracture
            • consider prophylactic nailing
        • radiation
          • 50 Gy pre-operative and 66 Gy postoperative is the standard dose for soft-tissue sarcomas
          • timing of radiation does not impact overall survival
    • Amputation
      • approach
        • level and incision guided by advanced imaging to ensure negative margins
      • technique
        • use of tourniquet without exsanguination
        • maintain meticulous hemostasis
        • meticulous dissection to ensure wide margins must confirm border free of disease with histology
          • frozen section can be used to ensure margins are free of tumor
    • Surgical resection of lung metastases
      • technique
        • wedge resection
        • lobectomy
  • Complications
    • Radiation-induced
      • pre-operative radiotherapy is associated with a 20-30% risk of wound complications
        • Risk of desquamation, delayed wound healing, infection
      • post-operative radiotherapy is associated with greater radiation-induced morbidity and an increased risk of radiation-induced sarcoma
        • Risk of later fibrosis, post-radiation fracture, possible secondary sarcoma
      • no difference in oncologic outcome between preoperative and postoperative radiation
      • late effects: fibrosis, post-radiation fracture, possible secondary sarcoma
      • post-radiation sarcoma
    • Recurrence
      • local recurrence <10% with radiation and surgery
      • following resection, the most common location for recurrence of a low-grade STS is locally
      • most recurrences occur in the first 5 years, but patients require indefinite follow-up
    • Unplanned excision
      • the most common mistake in treatment of soft tissue sarcomas
      • 74% have residual disease
      • CT chest, abdomen, pelvis to exclude metastasis
      • MRI of the limb to determine the degree of contamination, post-operative changes, and to assess margins
      • revision surgery
        • necessary for all unplanned excisions
        • limb salvage + radiation therapy
        • amputation
      • unplanned excision is associated with higher plastic reconstruction of the affected region
  • Prognosis
    • Natural history of disease
      • often slow-growing painless mass
      • metastasis is most commonly to the lung
      • 5% lymph node metastasis (most commonly epithelioid, synovial, angiosarcoma, rhabdomyosarcoma, clear cell)
    • Prognostic variables
      • tumor stage is most important prognostic factor
      • poor prognostic factors include
        • high-grade
        • metastatic disease
        • size > 5 cm
        • tumor location below the deep fascia
        • delay in diagnosis
        • unplanned excision
          • most common error in STS treatment
          • referral to orthopaedic oncologist for multidisciplinary workup and repeat excision is critical
    • Survival with treatment
      • low-grade disease: 90% 5-year survival
      • stage II and III disease: 50-75% 5-year survival 
      • stage IV: 15% 5-year survival
      • patients with advanced disease have median survival of 12-18 months
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