MRI diagnosis of solitary fibrous tumor in the orbit

Objective: To explore the MRI features of solitary fibrous tumor (SFT) in the orbit. Methods: The MRI findings of 7 patients with SFT in the orbit confirmed by histopathology were analyzed retrospectively. Results: Of the 7 lesions,5 occurred in the right orbit and 2 in the left orbit. Six lesions were located in the extraconal space near the lacrimal gland fossa, including 5 in the superomedial region and 1 in the inferolateral region. The other one was located in the retrobulbar intraconal space. The lesions with well-defined margin showed elliptic shape in 6 cases and lobulated configuration in 1. The maximum diameter of the lesions ranged from 18 to 40 mm (mean, 31 mm). The lesions showed homogeneous isointense relative to gray matter on T₁-weighted images in 6 patients. On T₂-weighted images, the lesions showed heterogeneous hypointense in 5 patients, isointense and hyperintense in one patient respectively. SFT demonstrated markedly homogeneous enhancement in 6 patients and inhomogeneous enhancement in one patient. The time-intensity curves (TIC) of 7 patients exhibited a rapidly enhancing and rapid washout pattern on dynamic contrast-enhanced (DCE) MRI. Conclusion: Hypointense signal on T₂WI, marked enhancement on contrast-enhanced T₁WI, and a rapidly enhancing and rapid washout pattern TIC on DCE MRI are the typical MRI features of orbital SFT. (authors)