Endoscopic Endonasal Approach to Intraconal Anaplastic Solitary Fibrous Tumor of the Orbit

Objective: Orbital solitary fibrous tumors (SFT) are exceptionally rare spindle-cell tumors which can be benign or malignant. Only a handful of dedifferentiated malignant orbital SFTs have been documented to date. Radical resection with open approach has been consistently utilized in the literature for these tumors.

Methods: We report utilizing the endoscopic endonasal approach (EEA) to biopsy and then surgically excise a malignant orbital SFT. We also present its unique pathological findings followed by a review of the English-language literature outlining the presentation, diagnosis, imaging, histopathology, management, and outcomes for these rare tumors.

Case Report: A 71-year-old woman presented with left-sided ptosis, mild diplopia, and intractable frontal headache. Magnetic Resonance Imaging (MRI) demonstrated a nodular, enhancing, intraconal orbital mass, ~1.8 × 1.6 cm in size, abutting the medial rectus muscle and optic nerve. An endoscopic endonasal approach with image guidance was employed, and a left-sided maxillary antrostomy, total ethmoidectomy, and sphenoidotomy was performed for complete exposure of the inferior and medial orbital walls. Oculoplastics and otolaryngology teams in conjunction removed the lamina as well as the inferomedial strut of the orbital floor. Periosteum was incised both medially and inferiorly to allow for fat to prolapse into the sinonasal cavity. With carful dissection, a hyperemic nodular mass involving the inferomedial orbit was visualized. It appeared to be well-encapsulated, and a biopsy was obtained and sent for permanent pathology which revealed anaplastic (dedifferentiated) SFT. After informed discussion regarding management options, patient elected to proceed with endoscopic resection over orbital exenteration.

During the second procedure, dissection separated the well-encapsulated tumor from the optic nerve, medial rectus, and skull base. It was removed entirely, and margins were taken including medially at the middle turbinate and posteriorly along the periorbita adjacent to the orbital apex. Final pathology was consistent with the initial biopsy, and all margins were negative for malignancy. Tumor cells revealed a strong positivity for BCL-2 and STAT6. Interestingly, heterologous rhabdomyosarcomatous elements were present, which is extremely rare in SFTs and to our knowledge has never been reported in the orbit. The case was presented at our multi-disciplinary tumor board conference, and the final recommendation was for adjuvant radiation with proton beam therapy.

Conclusion: An orbital SFT should be considered in the differential when patients present with a well-defined, enhancing orbital mass on imaging causing globe displacement. Surgical excision with clear margins is required for adequate local control of the tumor. In this report, we demonstrate that an EEA can be employed to surgically resect anatomically favorable orbital SFTs.

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Artikel online veröffentlicht:
15. Februar 2022