CT and MR imaging of a solitary fibrous tumor of the thigh

Solitary fibrous tumor is a rare mesenchymal tumor usually involving the pl eura. Extrapleural lesions may also occur. We report the CT and MRI appeara nce of a solitary fibrous tumor of the thigh. The imaging features as well as the histological and immunohistochemical characteristics are presented, especially its reactivity to the CD34 antigen. The tumor is most often beni gn, particularly in extra-pleural location, with good prognosis after total resection. Imaging is mainly useful to locate the tumor and assess its ext ension prior to surgery.