Orbital multiple myeloma: a diagnostic challenge.

Orbital involvement in multiple myeloma is unusual. We describe the case of an 85-year-old woman who presented with right eye proptosis, reduced visual acuity and diplopia. Computed tomography showed a lobulated, enhancing soft tissue mass arising from the right greater wing of the sphenoid with intraconal, lacrimal gland and ocular muscle involvement. Histopathology revealed predominantly atypical plasma cells in a background of reactive lymphocytes, with monoclonality towards kappa light chain protein, suggestive of multiple myeloma. This case illustrates the diagnostic imaging challenge of orbital multiple myeloma.