Soft Tissue Sarcomas Information

Summary

Soft Tissue Sarcomas are rare, malignant soft tissue 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: 7000 new case/year in the United States

Demographics: males > females; 85% occur in patients >15 years old

Anatomic location: 60% occur in extremities

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

Classification

Classification of STS is based on histology, with over 50 types recognized. All STS has 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)

AJCC staging system is used for interdisciplinary communication. AJCC Staging System for Soft Tissue Sarcoma of the Extremity or Trunk:

Presentation

History: may be a history of trauma that draws attention to the mass

Symptoms: slow growing, painless mass. Incidental trauma often draws attention to mass

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. Differentiation of whether a mass is above or below fascia has prognostic importance. Size > 5 cm in cross-section is a poor prognostic factor. Can be confused with more common pathology: lipoma, hematoma

Imaging

Radiographs: indications: obtain plain radiographs in at least two planes for initial workup

CT chest: indications: obtain to assess for metastatic disease

MRI: 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: lipoma, neurilemoma (schwannoma), intramuscular myxoma. If MRI is diagnostic and the mass is benign and symptomatic, then it can be removed without a biopsy. 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. Soft tissue sarcomas can look similar to hematomas, so be cautious of a "hematoma" which occurs without trauma

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: best results if done at the institution where definitive surgery will take place, under a multidisciplinary team.

Operative – wide surgical resection & radiation therapy: indications: standard of care in most cases. Treatment must be based on a tissue diagnosis unless images are diagnostic (i.e. lipoma). Radiation is an important adjunct to surgery decreasing local recurrence. Chemotherapy is controversial for soft tissue sarcomas. Considered standard of care for rhabdomyosarcoma and Ewing sarcoma. Outcomes: reduces risk of local recurrence to less than 10%.

Operative – 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.

Operative – 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.

Complications

Radiation induced: pre-operative radiotherapy is associated with a > 30% risk for wound complications. Post-operative radiotherapy is associated with greater radiation-induced morbidity and an increased risk of radiation-induced sarcoma. Early effects: desquamation, delayed wound healing, infection. Late effects: fibrosis, post-radiation fracture, possible secondary sarcoma. Postradiation sarcoma.

Recurrence: local recurrence <10% with radiation and surgery. Following resection, the most common location for recurrence of a low-grade STS is locally.

Unplanned excision: 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, 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: <10% local recurrence with surgery and radiation. Mortality up to 50% with high-grade disease.