A 52 year old male presented with changes in bowel movements, and a mass was detected on digital rectal exam.  Both CT and MRI revealed a large pelvic and gluteal mass filling the pelvic cavity displacing the adjacent pelvic structures.  After surgical removal, pathology revealed solitary fibrous tumor; a rare neoplasm uncommonly discovered in the thorax, and even less commonly in extrapleural locations.  We discuss in this article imaging findings and histological features of extrapleural solitary fibrous tumor.