We report an important and unusual cause of an enhancing retroperitoneal paracaval mass. Ten years after vena cava filter (VCF) placement, a 3.5-cm mass was found juxtaposed to the right kidney and vena cava. Open exploration demonstrated a venous variceal mass with perforation of the VCF through the wall of the vena cava, requiring vena cava resection and graft replacement. This is an infrequently described, potentially misleading and dangerous complication of vena cava filters. Better guidelines for such filters would be useful. We recommend an open approach in settings that could require similarly complex reconstructions.