Teenager with right groin mass

MRI of synovial sarcoma of groin
Axial (above right) and sagittal (below right) T2 MRI of the pelvis shows a well circumscribed soft tissue mass that is hyperintense compared to muscle and not clearly connected to any joint and that has some surrounding edema. Axial T1 MRI without contrast (above left) and axial T1 MRI with contrast (below left) show the mass to enhance homegenously.

The diagnosis was synovial sarcoma.