Solitary Fibrous Tumor of the Orbit: A Case Series With Clinicopathologic Correlation and Evaluation of STAT6 as a Diagnostic Marker

Abstract

Purpose: To retrospectively describe the clinical characteristics, management, and outcomes of a series of patients with solitary fibrous tumor (SFT) of the orbit and to evaluate signal transducer and activator of transcription 6 (STAT6) as a diagnostic marker.

Methods: Review of a retrospective, noncomparative, consecutive series of patients treated at a single institution with a histopathologic diagnosis of SFT. Demographic, clinical, and imaging data were collected, and paraffin-embedded tissue sections were stained to evaluate for the presence of STAT6 and other pertinent markers.

Results: Twenty-one patients were identified. Most presented with painless progressive proptosis or eyelid swelling for less than 6 months. Imaging revealed well-circumscribed, firm, variably vascular contrast-enhancing lesions with low to medium reflectivity on ultrasound. Four tumors were histopathologically malignant. All tumors were primarily excised, and 1 patient required exenteration. Two patients were treated with adjuvant radiation therapy. Six patients had recurrent disease of which 3 underwent repeat excision, and 2 were observed. No metastatic disease or attributable deaths were observed. All lesions with available tissue stained positively for both CD34 and STAT6.

Conclusion: This is the largest single institution case series of orbital SFT with clinicopathologic correlation and the largest series to confirm the presence of STAT6 in orbital lesions. The management of SFT remains challenging due to unpredictable tumor behavior, and complete excision is the generally recommended treatment. It remains unclear whether a subset of asymptomatic patients with histopathologically benign disease can be durably observed without negative sequelae.

Figure 1:

A 60 year old female presented with progressive proptosis and hypoglobus of the left eye complaining of upper lid swelling, diplopia, and intermittent pain (A). A 46 year old man presented with progressive fullness of the right upper eyelid, proptosis, and diplopia on upgaze. He also noted mild fluctuating erythema of the right upper eyelid (B).

Figure 2:

Computed tomography scan in the coronal (A) and axial planes (B) without contrast enhancement demonstrates a large intraconal and extraconal mass lesion which is isodense to the extraocular muscles and appears to be well-circumscribed with mass effect and anterior displacement of the left globe. Coronal (C) and axial (D) scans with contrast show avid enhancement of a well-circumscribed extraconal and intraconal lesion in the superomedial orbit with non-axial displacement of the globe.

Figure 3:

T1 weighted MRI in the coronal (A) and axial (B) planes without gadolinium showing a well-circumscribed intra and extraconal lesion that is isointense to the extraocular muscles and cerebral cortex. The same lesion enhances avidly and heterogeneously with gadolinium (C, D). T2 weighted MRI of the same lesion demonstrates heterogenous intensity and the mass appears ill-defined (E, F).

Figure 4:

Orbital echography demonstrates a well circumscribed lesion abutting the posterior globe on B-scan (A) and a well-defined, moderately to highly reflective lesion with heterogenous internal structure on A- scan (B).

Figure 5:

Anterior lid crease orbitotomy (A) for removal of a well-defined extraconal lesion with a smooth pseudocapsule (B). Transconjunctival medial orbitotomy with medial rectus takedown (C) for the removal of an enlongated mass with several bulbous excrescenses consistent with fibrous nodules. The lesion also has a smooth pseudocapsule (D).

Figure 6:

Histopathologic evaluation with hematoxylin and eosin staining demonstrates a whorled fibrous lesion with intervening cellularity and no defined pattern at 20× magnification (A). 40× magnification shows elongated spindle cells and some hyperchromatic nuclei without mitotic figures (B). The lesion stains avidly for CD34 (C) and STAT6 (D), both at 20' magnification.