Nonsecretory myeloma: analysis of two patients by immunoperoxidase studies and plaque-forming cell assay.

We studied the production and secretion of immunoglobulin by tumor cells in two patients with nonsecretory myeloma, by means of an immunoperoxidase technique and plaque-forming cell assay. Immunoperoxidase staining of bone marrow cells revealed monoclonal proliferation of immunoglobulin-containing cells, and the plaque-forming cell assay of peripheral mononuclear cells and bone marrow cells showed secretion of monoclonal immunoglobulin from the myeloma cells. These observations suggest that the secreted protein disappears as a result of enhanced catabolism or rapid deposition. There has been speculation as to the existence of this type of nonsecretory myeloma, but there had been no evidence. We were able to demonstrate it with the plaque-forming cell assay.