Retroperitoneal solitary fibrous tumor in a 62-year-old man. (A) CT scan shows huge retroperitoneal soft tissue mass on the right side of the bladder in uneven density. (B) The solid part in arterial phase is in moderate, uneven enhancement, with tumor vessel, and cystic areas of low density are visible inside. (C) The solid part in venous phase is in more significant, sustained, uneven enhancement, no enhancement in low-density cystic areas, but envelope enhancement is visible. (D) The tumor was composed of rich, dense, fusiform cells under the microscope, with branching vascular channels, collagenous bundles, and coagulation necrosis in focus areas.