Abstract

Solitary fibrous tumors (SFTs) most often involve the pleura and also may encompass the peritoneum and nonserosal sites. They occur as solitary encapsulated tumors and pursue a relatively benign clinical course. The usual criteria for malignancy are high cellularity, mitotic activity (more than 4 per 10 high-power fields), cellular pleomorphism, hemorrhage and necrosis as well as infiltrative growth. We report a case of malignant SFT of pleura who presented with an anterior mediastinal mass. Grossly, it was a 10x8x6.5 cm sized, encapsulated and well-demarcated, solid neoplasm with areas of extensive necrosis. Microscopically, parallel or haphazard arrangement of spindle cells with variable degrees of collagenous background were noted. Storiform fascicle formation, hemangiopericytoma-like pattern, and epithelioid cell clusters were often intermingled. Nodular areas with high cellularity and mitotic activity (> or =10/10 HPFs) were scattered throughout the neoplasm, however no definite cellular pleomorphism was encountered. Tumor cells were immunoreactive for vimentin and CD-34, which distinguished them from the mesothelial cells. Electron microscopically, they revealed fibroblastic and myofibroblastic differentiation.

• Keywords: Malignant solitary fibrous tumor;Pleura;Mediastinum;CD-34;Electron micro-scopy