Solitary fibrous tumor of the orbit: an unusual cause of unilateral proptosis. Case report with a review of the literature

Background: The solitary fibrous tumor (SFT) is a spindle-cell tumor that very rarely involves the orbit. We report a new case that we compare to reports in the literature.

Methods: A 72-year-old woman presented a conjunctival inflammation of the right eye developing over 5 months with progressive proptosis. Magnetic resonance imaging revealed an extraconal and homogeneous mass, which showed hypointensity on T1-weighted images and hyperintensity on T2-weighted images, without specificity. Histological examination of the lesion removed by anterior orbitotomy confirmed the diagnosis of the SFT of the orbit. The patient was doing well without recurrence after 9 months.

Conclusions: The diagnosis of SFT is histological. It is a mesenchymal tumor. Immunohistochemically, the tumor cells are strongly positive for CD34 and vimentin. Conclusions: The SFT of the orbit is a very rare and generally benign tumor. It must be immunohistochemically differentiated from other spindle-cell tumors of the orbit. The treatment is a complete surgical excision, and long-term follow-up is necessary because recurrence may appear long after treatment.