Orbital melanocytoma.

PURPOSE: To report a case of intermediate grade meningeal melanocytoma presenting as a recurrent orbital mass.

INTRODUCTION: Melanocytomas are rare, primary, pigmented tumors of the central nervous system, usually presenting as well-circumscribed, encapsulated, solid masses in the posterior cranial fossa and at the spinal region, often attached to the underlying dura. Orbital manifestation is rarely encountered.

METHODS: Case report with computed tomography scan, magnetic resonance imaging, histology, and immunohistochemistry.

RESULTS: A 40-year-old man presented with a recurrent orbital mass manifesting as progressive proptosis of the right eye of 4 years duration. The computed tomography scan and magnetic resonance imaging revealed an intraconal mass in the superior quadrant of the orbit. Histological analysis of the excision biopsy of the mass showed a highly cellular, locally infiltrating melanocytic neoplasm suggestive of an intermediate grade meningeal melanocytoma. Immunohistochemical staining for S-100 protein and HMB-45 monoclonal antibody confirmed the diagnosis.

CONCLUSIONS: Recurrent intermediate grade orbital melanocytomas are rarely encountered and have to be distinguished from other topographically similar primary melanotic tumors. They have to be managed more aggressively if intracranial extension is present due to its close relation to the visual pathways.