RESUMO
A solitary fibrous tumor is a rare spindle cell neoplasm originating from the mesenchyme. This type of tumor of the orbit is very uncommon and can be misdiagnosed as a hemangiopericytoma, fibrous histiocytoma, meningioma, or neurofibroma. We report an orbital solitary fibrous tumor in an 18-year-old male, with slow-growing swelling in the right orbital region. An orbital contrast-enhanced computed tomography scan showed heterogeneously enhancing right extraconal inferomedial mass, with no evidence of calcification or bone destruction. The lesion was surgically excised without complications. Based on microscopic and immunohistochemical findings, the mass was finally diagnosed as a solitary fibrous tumor. These tumors should be preoperatively differentiated from other spindle cell tumors of the orbit, and radiological imaging methods are useful in the differential diagnosis but are nonspecific. Therefore, histopathological and immunohistochemical staining features are more useful for the diagnosis of solitary fibrous tumors, especially CD34 staining