Computed tomography and appearance of cystic orbital solitary fibrous tumor. A, Axial computed tomography showing a septate, cystic mass of the anteromedial right orbit. B, Preoperative photograph showing right inferolateral dystopia, upper eyelid swelling, and ptosis. C, Symmetric cosmetic appearance after tumor excision.
Histopathology of cystic orbital solitary fibrous tumor. A, Solitary fibrous tumor with a pseudocapsule and septa (hematoxylin-eosin, original magnification ×20). B, Spindle cells in hypocellular and hypercellular areas and perivascular fibrosis (hematoxylin-eosin, original magnification ×300). C, CD99-immunopositive tumor cells lining the septal surface (asterisk) and permeating the pseudocapsule (original magnification ×100). D, CD34 immunopositivity (original magnification ×400). E, Bcl-2–immunoreactive cells in and along the septal surfaces (original magnification ×400).
Feuerman JM, Flint A, Elner VM. Cystic Solitary Fibrous Tumor of the Orbit. Arch Ophthalmol. 2010;128(3):385-387. doi:10.1001/archophthalmol.2009.405
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Solitary fibrous tumor (SFT) is a rare spindle cell tumor of mesenchymal origin, most commonly arising from the pleura but also known to occur in extrapleural sites.1 Orbital SFT was first described in 1994,2 and since then approximately 70 orbital cases have been published in the literature. Virtually all reported cases of orbital SFT to date were solid tumors.3 We report the first case to our knowledge of an entirely cystic SFT arising in the orbit.
A 45-year-old woman had painless right upper eyelid puffiness for 1 year, vision-obstructing ptosis on the right for 6 months, diplopia on left gaze, epiphora, and crusting. On examination, visual acuity was 20/20 OU. There was diplopia at 60° of left gaze. The right eye was dystopic 2 mm laterally and 1 to 2 mm inferiorly with 1 mm of proptosis (Figure 1). An ill-defined softness was palpated superomedially in the right orbit.
Orbital computed tomography revealed a well-defined 2.3 × 1.1 × 1.9-cm cystic mass in the medial aspect of the right orbit with central rim–enhancing fluid hypodensity, central septations, and a 3-mm nodule medially (Figure 1). There was subtle remodeling of the lamina papyracea.
The patient underwent transcaruncular orbitotomy. A 1.8 × 1.1 × 1.5-cm cystic, translucent, blue-gray mass with small amounts of adherent yellow-tan tissue was transected from a thin stalk at its posterior-superior pole. On opening the wall of the mass, prompt deflation with copious straw-colored fluid was noted.
The tumor was pseudoencapsulated, was circumscribed, and had multiple septa (Figure 2). Microscopically, the capsule and septa exhibited features typical of SFT.2,4 There were bland spindle cells haphazardly arranged, without a tendency to form bundles. Some regions were highly cellular, while other regions were hypocellular with abundant matrix and deposition of thick collagen fibers (Figure 2). There was characteristic perivascular fibrosis, particularly in hypocellular areas. Vascularity was rich with dilated vessels and small capillary-sized vessels. Pleomorphism, tumor giant cells, and mitotic activity were absent. The tumor cells formed and lined the septa, indicating that the tumor was really a pseudocyst. The tumor cells also invaded through the pseudocapsule, reaching the resection margin multifocally. The tumor cells stained positively for immunoreactive vimentin, CD99, CD34, and Bcl-2 (Figure 2). Fibroblasts, including those forming the pseudocapsule, did not stain with CD99, CD34, or Bcl-2. Tumor cells showed no S-100 protein, glial fibrillary acidic protein, epithelial membrane antigen, neurofilament, smooth muscle–specific actin, or desmin immunoreactivity.
Postoperatively, the patient experienced complete resolution of her eyelid swelling, ptosis, diplopia, dystopia, epiphora, and crusting.
Orbital SFT typically causes insidious, painless proptosis developing over an average of 2 years in patients averaging 40-years-old (age range, 9-76 years).3,4 Treatment consists of excision of the circumscribed growth, but local recurrences due to incomplete excision can occur.3,4 In our case, microscopic invasion through the pseudocapsule may theoretically permit recurrence. A case of malignant orbital SFT also has been reported.5
There is a single report of an orbital SFT that was mostly solid with some cystic components.3 Entirely cystic SFT has been described in other extrapleural locations6 but never in the orbit. To our knowledge, our case is the first reported case of an entirely cystic SFT arising from the orbit. The fact that tumor cells rather than endothelium lined the septa probably contributed to the pseudocystic fluid accumulation.
The main differential diagnosis in this case was cystic schwannoma and giant cell angiofibroma. The tumor was negative for S-100 protein and neurofilament stains, and there were no giant cells. These findings support a diagnosis of SFT. We recommend that SFT be considered in the differential diagnosis of cystic orbital lesions.
Correspondence: Dr Elner, Kellogg Eye Center, University of Michigan, 1000 Wall St, Ann Arbor, MI 48105 (firstname.lastname@example.org).
Financial Disclosure: None reported.
Funding/Support: This work was supported by grants EY09441 and EY007003 from the National Institutes of Health.