Findings: Contrast CT. Large, heterogeneous enhancing soft tissue mass with poorly-defined margins, closely related to the aortic root and atrioventricular groove. Intra-lesional hypervascularity (arrows) is evident. PET/CT. Intense FDG uptake in the mass; MIBG scan also showed uptake in this region. Cardiac MRI. Steady-state free precession bright blood images demonstrate the mass to be intra-pericardial in location, extending into the atrioventricular (AV) groove.