Solitary fibrous tumor in the retroperitoneal space: report of a case.

Solitary fibrous tumors (SFTs) are spindle-cell neoplasms originally described in the pleura. It is now known that these tumors can develop in many sites. This report describes the case of a well-circumscribed tumor located around the superior mesenteric artery (SMA), which was initially thought to be either a superior SMA aneurysm, a lymphoma, or a neurogenic tumor. Histological examination demonstrated the tumor to be composed of a cellular proliferation of ovoid to spindle cells with a fine collagenous matrix in the short fascicles. Immunohistochemical staining was strongly positive for CD34 and negative for factor VIII, cytokeratin, desmin, and muscle-specific actin (HHF-35). These findings suggested a diagnosis of SFT in the retroperitoneal space. To our knowledge, this is the first report of an SFT located around the SMA. Based on the above findings, it is important to include SFT in the differential diagnosis of retroperitoneal tumors located around the SMA.