Delayed PET/CT of Pericardial Synovial Sarcoma.

Pericardial synovial sarcoma is a rare malignancy. We report the case of a patient who was referred to our institution for a large pericardial effusion requiring pericardiocentesis. CT imaging revealed an inhomogeneous pericardial mass beside the right atrium, and then a PET/CT scan was performed. Standard images were inconclusive whether delayed images showed an FDG-avid pericardial lesion that was surgically removed with histological diagnosis of a poorly differentiated biphasic synovial sarcoma. When considering mediastinal or pericardial mass, a delayed PET/CT may improve lesion-to-background contrast by reducing blood pool activity.