A case of orbital solitary fibrous tumor.

BACKGROUND Solitary fibrous tumor is a spindle cell neoplasm that most commonly arises in the pleura and very rarely involves the orbit. CASE A 38-year-old woman presented with slowly progressive proptosis of 3 months duration and optic nerve head edema in her right eye. Magnetic resonance imaging revealed a well-circumscribed, round mass lesion, which showed isointensity to the gray matter in a T1-weighted image, and variegated intensity in a T2-weighted image and contact with the optic nerve in her right orbit. The tumor was successfully removed by anterior orbitotomy. OBSERVATIONS The tumor showed a "patternless pattern" of tumor cell arrangement, alternating hypercellular and hypocellular areas, a hemangiopericytoma-like pattern, and thickened strands of collagen. Immunohistochemically, the tumor cells were positive for CD34 and vimentin, and all were negative for other markers of epithelial, neural, muscular, histiocytic, and vascular endothelial cell elements. The tumor was diagnosed as a solitary fibrous tumor, and the patient was doing well with no evidence of recurrence 15 months after surgery. CONCLUSIONS This case was the 19th reported case of solitary fibrous tumor in the orbital region. CD34 is a highly sensitive marker for solitary fibrous tumor.