Bone marrow aspirate immunofluorescent and bone marrow biopsy immunoperoxidase staining of plasma cells in histologically occult plasma cell proliferative marrow disorders.

Immunofluorescent staining (immunofluorescence bone marrow aspirate) and immunoperoxidase staining (immunoperoxidase bone marrow biopsy) were compared in 26 patients with plasma cell dyscrasia and less than 10% marrow plasma cells. Their clinical diagnoses included monoclonal gammopathy of undetermined significance (13 patients), treated multiple myeloma (four patients), multiple myeloma with less than 10% marrow plasma cells (two patients), primary systemic amyloidosis (two patients), monoclonal gammopathy of undetermined significance with neuropathy (two patients), angiofollicular lymph node hyperplasia (two patients, all with the POEMS [polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes] syndrome), and primary (amyloidosis) amyloid neuropathy (one patient). The percentage of plasma cells was greater than 5% in 23% of patients and less than or equal to 5% in 77% of patients. With immunofluorescence bone marrow aspirate and immunoperoxidase bone marrow biopsy, light-chain restriction was demonstrated in 84% of all cases and accurately determined in 96% of all cases as shown by serum and urine paraprotein analysis or tissue amyloid typing. Monoclonal populations of plasma cells can be readily identified with immunofluorescence bone marrow aspirate and immunoperoxidase bone marrow biopsy in most patients with paraproteins and marrow plasmacytoses not diagnostic of multiple myeloma.