Bilateral primary extramedullary orbital plasmacytomas.

An 81-year-old man presented with bilateral orbital tumors that were found to be extramedullary plasmacytomas. Immunoperoxidase staining of the tissue was positive for IgG-kappa; no lambda chains were seen. Results of serum immunoelectrophoresis were positive for monoclonal IgG-kappa. Test results of the urine were positive for Bence Jones protein; only kappa chains were seen on radial diffusion. Systemic evaluation failed to show tumor elsewhere. The patient was treated with radiation and low-dose melphalan/prednisone, with good response. Five years later, the results of immunoelectrophoresis are normal and there is no clinical evidence of tumor; however, a small amount of kappa light chains remains in the urine. This case supports the important therapeutic and prognostic differences among orbital involvement in extramedullary plasmacytoma, solitary myeloma of bone, and multiple myeloma.