Myxoid solitary fibrous tumor of the retroperitoneum: MRI findings with the pathologic correlation.

We report here on a case of solitary fibrous tumor of the retroperitoneum, and the tumor displayed a predominantly myxoid histology. A 56-year-old man presented with an incidentally detected retroperitoneal mass. On the MR images, the mass was observed as having iso-signal intensity on the T1-weighted images and high signal intensity on the fat-saturated T2-weighted images. The mass showed intense enhancement on the Gd-DTPA enhanced T1-weighted images. At surgery, a well-defined solid mass was found in the left retroperitoneum. The histological diagnosis was made as solitary fibrous tumor with a predominantly myxoid histology.