Giant solitary fibrous tumor arising from greater omentum.

Extrathoracic solitary fibrous tumors (SFTs) have been described at almost every anatomic location of human body, but reports of SFT in the abdominal cavity are rare. We herein present a rare case of SFT originating from greater omentum. Computed tomography revealed a 15.8 cm × 21.0 cm solid mass located at superior aspect of stomach. Open laparotomy confirmed its mesenchymal origin. Microscopically, its tissue was composed of non-organized and spindle-shaped cells exhibiting atypical nuclei, which were divided up by branching vessel and collagen bundles. Immunohistochemical staining showed that this tumor was negative for CD117, CD99, CD68, cytokeratin, calretinin, desmin, epithelial membrane antigen, F8 and S-100, but positive for CD34, bcl-2, α-smooth muscle actin and vimentin. The patient presented no evidence of recurrence during follow-up. SFT arising from abdominal cavity can be diagnosed by histological findings and immunohistochemical markers, especially for CD34 and bcl-2 positive cases.