Optic nerve glioma: A great mimicker

BACKGROUND: Arachnoid proliferation, although rare, is known to occur in association with optic gliomas. However, chondroid and chordoid metaplasia has not been reported previously. CASE DESCRIPTION: A 27-year-old male presented with progressive, painless loss of vision in right eye, associated with vomiting and headache for one and a half months. Computed tomography (CT) scan revealed a contrast enhancing mass arising from planum sphenoidale. Perioperative findings showed the tumor adherent to the right optic nerve and attached to basal dura and falx. A clinical impression of an intradural, optic nerve sheath meningioma was made. Histopathological examination revealed a glial tumor with adjacent areas displaying marked fibroblastic and arachnoid cell proliferation with chondroid as well as chordoid differentiation along with myxoid change and dense collagenisation. Reticulin stain, immunochemistry with glial fibrillary acid protein (GFAP), epithelial membrane antigen (EMA), and S-100 helped to arrive at the final diagnosis of optic glioma displaying exuberant arachnoid proliferation with cartilaginous metaplasia. CONCLUSION: We report a case of optic nerve glioma displaying extensive arachnoid proliferation, chordoid, and cartilaginous metaplasia, which mimicked chondrosarcoma or chordoid meningioma, posing a diagnostic dilemma. A clinical feedback, simple reticulin stain, and GFAP staining is of immense value in such cases to arrive at the correct diagnosis.