Case report: amyloid tumors in a case of non-secretory multiple myeloma.

Multiple myeloma (MM) is a neoplastic disorder characterized by proliferation of a single clone of plasma cells derived from B cells, which proliferates in the bone marrow and frequently invades the adjacent bone, producing skeletal destruction that results in bone pain and fractures. Patients with MM can furthermore present with anemia, hypercalcemia and renal failure. Non-secretory multiple myeloma (NSMM) is characterized by the absence of a monoclonal (M) protein in both the serum and urine. The reported incidence is 1-5% of all multiple myeloma cases. Development of amyloid tumors in NSMM has been described in the literature only occasionally. The clinical features of a 49-year-old female patient with NSMM and amyloid tumors in the breast, lung and rib are presented in this report. Conventional histology, Congo red staining with and without potassium permanganate pretreatment, aldehyde bisulfite-toluidine blue (ABT) reaction, sialic acid specific topo-optical reaction, toluidine blue topo-optical reaction as well as immunohistochemistry were performed. An attempt is made to explain the lack of monoclonal immunoglobulins in the serum and urine, although extensive organ amyloidosis of AL type (kappa-light chains) has been found. It is assumed that the plasmocytic plasma cells possess an excretory mechanism, which allows the pathologic immunoglobulins to be secreted either as amyloid proteins polymerizing into amyloid fibrils, or as immunoglobulin fragments that are subject to degradation as soon as they are excreted out of the tumor cell. In this paper, we review the occurrence of amyloid tumors in non-secretory multiple myeloma and, in a single case report, we confirm the existence of carbohydrate residues, including sialic acids and sulfated GAGs, in amyloid deposits.