Malignant, high-grade, soft-tissue neoplasms that usually arise in close association with tendon sheaths, bursae, and joint cavities.
Cell of origin is unclear.
Less than 10% are intraarticular.
Account for 7-8% of all malignant soft-tissue tumors and are the most common nonrhabdomyosarcomas soft-tissue sarcomas in children.
Most common location is the lower extremity, followed by upper extremity, trunk, abdomen and head and neck.
Approximately 30% of patients are younger than 20 years of age.
Most cases in patients between the ages of 20-40’s.
Presentation usually of a deep seated mass that has been present for a number of years.
4th most common soft tissue sarcoma.
Histological has a biphasic differentiation with epithelial-like and spindle cells.
Can have a monophasic pattern with only spindles cells or rarely epithelial-like cells.
Immunohistochemical tests help in the diagnosis by indicating positive reactions for keratin and epithelial membrane antigen, differentiating the lesion from other sarcomas.
Most common site for metastases is the lung, and survival with metastatic disease is rare.
Surgical resection treatment of choice.
5-year survival rates range from 57-63%.
10 year survival 11-30%.
Risk factors with poor prognosis include advanced stage, male gender, tumor grade and truncal location of the tumor.
Majority of lesion develop in the vicinity of the large joints of the extremities with 60-70% involving the lower extremities, especially around the knees and thighs.
Chromosomal translocation of chromosome X;18 appears to be the primary pathogenic event.
Chromosomal translocation of X;18 leads to the formation of SYT-SSX1 or SSX2 fusion genes.
SYT encodes for a transcription factor and SSX1 and SSX2 genes produce transcriptional inhibitor proteins.
The specific type of translocation present is correlated with prognosis.
Adjuvant radiation considered for high risk patients.
Intra-abdominal synovial sarcomas account for less than 1% of lesions.
Local recurrence is associated with an increased risk of systemic relapse and decreased disease-free survival.
Tumor free margins are recommended to be 1 to 3 cm in adults.