Extrapleual solitary fibrous tumors:a clinicopathologic study of 39 cases

Purpose To investigate the clinicopathologic and immunohistochemical features of extrapleural solitary fibrous tumors (E-SFT) and their biologic behaviors. Methods The clinical pathologic data were reviewed retrospectively and immunohistochmical stains were performed in 39 case of E-SFT. Results 25 cases were females and 14 cases were males,affected age ranged from 15 to 81 years (mean,41.2 years). The sites of E-SFT involvement were soft tissue (15 cases),orbit (8 cases),retroperitoneum (4 cases),pelvis (3 cases),cranial cavity (4 cases),kidney (2 cases),urinary bladder (1 case),lung (1 case),and nasal cavity (1 case). Histologically,the tumors showed a wide range of growth patterns,varied form predominantly fibrous lesions containing large collagenized areas to more cellular and less fibrous areas,with thick-walled branching vessels showing HPC-like growth pattern. Myxoid degeneration and fat-forming areas were noted. There were four categories,including fibrous SFT,cellular SFT,giant-cell-rich SFT and fat-forming SFT. Immunohistochemically,all cases of the tumor cells showed diffusely and strongly positive for both vimentin and CD34,less frequently positive for CD99 (20/24),bcl-2 (18/24). Conclusion SFTs are rare mesenchymal spindle cell tumors,which could be found in various sites of human body and need to be distinguished from other spindle cell tumors.