Atypical location of a rare tumor: orbital myopericytoma.

A 46-year-old man presented with a 2-year history of progressive visual acuity loss in his right eye. A computed tomography (CT) scan revealed a well-circumscribed, isodense intraconal lesion at the apex of the right orbit. Magnetic resonance imaging (MRI) showed a solid, hyperintense lesion on T2-weighted images with heterogeneous enhancement after gadolinium contrast administration. The resection of the mass was performed via a lateral orbitotomy. Complete excision was not possible due to dense adhesions to deep structures, and intraoperative manipulations to dissect the tumor from its attachments caused circular pupillary dilation. That could be a sign that the vascular supply to the ciliary ganglion is compromised, which is closely related to the vascular supply of the optic nerve. Pathological examination revealed a neoplasm composed of perivascular spindle cells arranged in a concentric fashion. By immunohistochemistry, the cells were positive for smooth muscle actin and focally for desmin. These findings were compatible with a diagnosis of myopericytoma. Postoperatively, the patient developed severe orbital congestion, which resolved with treatment. His visual acuity and overall clinical course improved over time.