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E1149. Synovial Sarcoma: Common and Atypical Imaging Features and Locations
Authors
  1. Kenneth Huynh; Mayo Clinic - Scottsdale
  2. Ba Nguyen; Mayo Clinic - Scottsdale
Background
Synovial sarcoma (SS) is a rare, high-grade mesenchymal tumor accounting for up to 10% of sarcomas. Despite its appellation inaccurately indicating a synovial involvement, SS is found in only a small percentage of cases in the peri-articular/intra-articular locations. The SS, ubiquitous throughout the body, may initially be indolent and mimic a benign process. Synovial sarcoma is characterized by the triple features of solid, necrotic-hemorrhagic-cystic and fibrous components with high cellular vascularity and a propensity for rapid metastasis and recurrences. Familiarity with the imaging features of SS may help differentiate the aggressive process from benign peri-articular masses and cystic lesions that are similar in appearance.

Educational Goals / Teaching Points
1. To present the etiology and histopathology of synovial sarcoma with three main variants: monophasic, biphasic, and poorly differentiated types. 2. To review the anatomic and functional characteristics of synovial sarcoma mostly with PET/CT documenting the common and atypical features, metastatic patterns, and post-therapeutic surveillance.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
This exhibit will present characteristic imaging features of synovial sarcoma on MR, CT, US, and PET/CT. MR is the modality of choice for characterizing SS, with 55% of cases presenting with the “triple sign” and “bowl of grapes” appearance. CT is useful for detecting calcification and bone involvement, as well as assessing for areas of metastasis. Functional imaging of SS with PET demonstrates an F-18 FDG-avid lesion with particular benefit in the role of initial staging, prognosis, and post-therapeutic surveillance. Common and atypical primary sites, such as larynx, superior vena cava, right atrium, pericardium, mediastinum, pleura, lung, peritoneum, kidney, pelvic wall, prostate, hip, thigh, knee, along with their metastatic patterns are reviewed.

Conclusion
The viewers will be able to recognize characteristic features and presentations of synovial sarcoma through multiple imaging modalities, along with its common and atypical locations.