Immunofluorescent and immunoperoxidase characteristics of IgDlambda myeloma involving the orbit.

A biopsy specimen from a 59-year-old man with unilateral proptosis revealed an orbital plasmacytic tumor. In vitro immunoperoxidase and immunofluorescence studies and direct immunoperoxidase staining of Bouin's fixed, paraffin-embedded tissue sections demonstrated that the tumor consisted of plasma cells with surface and intracellular IgDlambda immunoglobulin. Systemic evaluation demonstrated multiple myeloma. A review of previously published reports combined with the case presented here suggests that IgD myeloma has a predilection for orbital involvement. Thus, while IgD myeloma accounts for only 2% of all myelomas, it may account for a significant percentage of myelomas with orbital involvement. The distinctive clinical course of IgD myeloma, particularly its poor prognosis, warrants consideration of the immunologic and serologic findings in patients with orbital involvement by myeloma. The application of immunofluorescence and immunoperoxidase techniques to the study of orbital lymphoreticular neoplasms should result in a clearer understanding of these neoplasms.