Conventional and advanced MR imaging insights of synovial sarcoma

Objectives: Synovial sarcomas commonly involve extremities. The purpose of this study was to systematically assess and describe the appearance of pathologically proven synovial sarcomas on conventional MR sequences, diffusion weighted imaging and dynamic contrast enhanced imaging. Methods: In this cross-sectional retrospective study, fifteen pre-operative MRIs were analyzed separately by two musculoskeletal radiologists and a fellow. MRI features of synovial sarcomas were evaluated in a systematic fashion on conventional and advanced MR sequences. Results: The tumors demonstrated heterogeneous appearance on conventional MR sequences. Peritumoral edema was absent in four of 15 (27%) lesions including grade 2 and grade 3 tumors. Average minimum ADC was 0.8 × 10–3 mm²/s and average mean ADC was 1.2 × 10–3 mm²/s. There was avid early arterial phase enhancement on contrast imaging. Average relative enhancement of the tumors was 5.7 times compared to the adjacent skeletal muscle. Conclusion: Synovial sarcomas demonstrate avid early arterial phase post-contrast enhancement on contrast images, low ADC values, and heterogeneous appearance on conventional MRI sequences. Peritumoral edema may be absent in such tumors despite being high grade tumors.