Schwannoma of the Orbit

Abstract

Background: A schwannoma is a benign, slow-growing peripheral nerve sheath tumor that originates from Schwann cells. Orbital schwannomas are rare, accounting for only 1% of all orbital neoplasms. In this study, we retrospectively review orbital schwannomas and characterize clinical, radiologic, and histologic features of this rare entity.

Methods: A retrospective review was performed to identify patients with histologically confirmed orbital schwannoma, among a list of 437 patients who had visited our hospital with soft tissue masses within the orbit as the primary presentation between 2010 and 2014. Patient charts and medical records were reviewed for demographic information, relevant medical and family history, physical examination findings relating to ocular and extraocular sensorimotor function, operative details, postoperative complications, pathologic report, and recurrence.

Results: Five patients (5/437, 1.1%) were identified as having histologically confirmed orbital schwannoma and underwent complete excision. Both computed tomography (CT) and magnetic resonance imaging (MRI) studies were not consistent in predicting histologic diagnosis. There were no complications, and none of the patients experienced significant scar formation. In two cases, patients exhibited a mild postoperative numbness of the forehead, but the patients demonstrated full recovery of sensation within 3 months after the operation. None of the five patients have experienced recurrence.

Conclusion: Orbital schwannomas are relatively rare tumors. Preoperative diagnosis is difficult because of its variable presentation and location. Appropriate early assessment of orbital tumors by CT or MRI and prompt management is warranted to prevent the development of severe complications. Therefore, orbital schwannomas should be considered in the differential diagnosis of slow-growing orbital masses.

Keywords: Neurilemmoma; Orbital neoplasm; Schwann cells; Surgery.

Fig. 1. Case 1. This 51-year-old woman presented with an eight-year history of a progressively enlarging mass on her right upper eyelid (white arrows). (A) Preoperative axial computed tomography (CT) image. (B) Preoperative coronal CT image. (C) Preoperative photograph. (D) Intraoperative photograph showing the mass. (E) Photomicrograph of a tumor specimen showing a biphasic pattern of Antoni A areas (black arrow) with Verocay bodies and Antoni B areas (blue arrow) (H&E, ×40). (F) Immunohistochemical analysis showing positive staining for S-100 protein (S-100, ×100). (G) Postoperative axial CT image. (H) Postoperative coronal CT image. (I) Follow-up photograph at five months.

Fig. 2. Case 2. This 31-year-old woman presented with a five-year history of a slowly enlarging, palpable, and painless mass in her left lower eyelid (white arrows). (A) Preoperative axial computed tomography (CT) image. (B) Preoperative coronal CT image. (C) Preoperative photograph. (D) Intraoperative photograph showing the mass. (E) Photomicrograph of a tumor specimen showing typical manifestation of schwannoma with Antoni A areas (black arrow) containing Verocay bodies and Antoni B areas (blue arrow) (H&E, ×40). (F) Immunohistochemical analysis showing positive staining for S-100 protein (S-100, ×40). (G) Postoperative axial CT image. (H) Postoperative coronal CT image. (I) Follow-up photograph at eight months.