Objective    To study the clinicopathologic and immunohistochemical features of solitary fibrous tumor (SFT) and its biologic behavior.     Methods    Clinicopathologic data of 8 cases of SFT were collected and analyzed. Immunohistochemical staining (Envision method) for CD34

vimentin

CD99

bcl-2

S-100 and SMA was performed in the specimens collected from January 2003 to June 2006 in our hospital.     Results    Eight patients

5 male and 3 female

aged from 31 and 62 years (mean 45.3). SFTs located in mediastinum

nasal cavity

parotid

oral cavity and orbital cavity. The main clinical manifestations were local mass and pressure symptom. The diameter of SFTs was between 1.5 cm and 25.0 cm and clear edge in most SFTs. The characteristic features under microscope included patternless growth pattern

alternating hypercellular and hypocellular areas

blunt spindle cells within keloidlike hyalinization

and hemangiopericytoma-like regions. Positive immunohistochemical staining was vimentin 8

CD34 7

bcl-2 6

CD99 7

SMA 4

S-100 1.     Conclusion    SFT is a rare mesenchymal spindle cell tumor

occurring in various parts of human body. It needs to be distinguished from other spindle cell tumors

and the immunophenotype can be of help in differential diagnosis. Minority of SFTs has malignant behavior

manifesting as local recurrence or metastasis. The behavior of SFT is unpredictable

requiring a careful

long-term follow-up.