Isolated Orbital Plasmacytoma with Progression to Multiple Myeloma: A Case Presentation

Extramedullary plasmacytoma is a subset of plasma cell tumors, and it accounts for 3% of all plasma cell tumors. Extramedullary plasmacytoma originate in the head and neck region and most commonly affect the extracranial nasal sinuses. The literature is scant of reports of extramedullary plasmacytoma to the orbit. Our institution reports a patient's clinical presentation, workup, pathological findings and postoperative course of an orbital extramedullary plasmacytoma.

A 62 year-old right-handed dominant man with known history of HIV was referred from ophthalmology with 3 months of progressive right eye symptoms including diplopia, proptosis, and diminished ocular motility. Clinical examination revealed a right 6th cranial nerve deficit with lateral gaze palsy, chemosis, proptosis, and diminished visual acuity of the right eye. Imaging of the brain showed an extra-axial lesion extending from the tip of the lesser wing of the sphenoid into the right orbit with mass effect. An additional extra-axial lesion in the left frontal anterior lobe of the brain appeared suspicious for an en plaque meningioma. The patient underwent a right cranio-orbitozygomatic craniotomy with orbital reconstruction for complete resection of the orbital mass. Intraoperative preliminary pathology was suggestive of a highly cellular neoplastic tumor, which was possibly a malignant meningioma or lymphoma. Final pathological diagnosis of the tumor was consistent with intraorbital extramedullary plasmacytoma. Immunohistochemistry of the tumor revealed sheets of neoplastic plasma cells with cytoplasmic IgG kappa light chain reaction. Standard multiple myeloma assessment identified elevated beta-2 microglobulin and protein electrophoresis levels. Nuclear body imaging and whole body skeletal survey revealed uptake of Technetium-99m in the left frontal skull and no obvious lytic or boney destructive processes, respectively. Postoperative treatment included an extended course of chemotherapy. A recent bone marrow biopsy of the left iliac crest revealed 2% monoclonal plasma cell population with cytoplasmic IgG kappa light chain restriction.

The literature is very scarce with reports of solitary extramedullary plasmacytoma of the orbit. This type of tumor is a rare subtype of plasma cell tumors. Isolated proliferation of plasma cell has a good chance of recovery, but conversion to multiple myeloma can worsen the prognosis with mean survival time of approximately 3 years.