title: Differentiation of monoclonal gammopathy of undetermined significance and multiple myeloma using flow cytometric characteristics of plasma cells.
abstract: OBJECTIVE
  The differential diagnosis between multiple myeloma (MM) and monoclonal gammopathy of undetermined significance (MGUS) may be uncertain in some cases; this problem is reflected by discrepancies between different classification systems with an accordance in only 2/3 of cases. We studied whether flow-cytometric characteristics of plasma cells (PC) can be used for the differentiation between MGUS and MM.
  
  
  METHODS
  Patients were divided into 3 groups: Group A included 13 myeloma patients with a plasma cell infiltration of the bone marrow of 10-30%, serum M-protein < or = 3.5 g/dL (IgG) or < or = 2 g/dl (IgA) and without bone lesions in conventional radiography. Group B consisted of 53 patients who fulfilled the Durie and Salmon diagnostic criteria including at least one major criterion, and group C individuals with MGUS (n=17). The ratio of immunophenotypically normal (i.e. CD19(+)/CD56(-)) to all bone marrow plasma cells (BMPC), the number of peripheral blood PC (PBPC), the percentage of BMPC in S-phase and the DNA content of BMPC were analyzed.
  
  
  RESULTS
  All individuals with MGUS and no patient with MM in group A or group B had a ratio of phenotypically normal to all BMPC > or = 20%. The median of monoclonal PBPC was 0/microL (range 0-2/ microL) in MGUS, 1/microL (range 0-30/microL) in MM group A and 2.4/microL (range 0-211/microL) in MM group B. The median percentage of BMPC in S-phase was 1.6% both in MGUS and in group A and 3% in group B. Aneuploidy was found in 12%, 11% and 41% in MGUS, group A and group B, respectively.
  
  
  CONCLUSIONS
  The ratio of immunophenotypically normal to all BMPC was the only flow-cytometric parameter for the differentiation of MGUS and MM group A (p<0.0005). The other parameters were significantly different between MGUS and MM group B, but not group A.
authors.affiliation: Department of Hematology and Oncology, Universitätsklinikum Charité, Humboldt-Universität Berlin, Germany. sezer@charite.de
authors.forename: O
authors.initials: O
authors.lastname: Sezer
authors.forename: U
authors.initials: U
authors.lastname: Heider
authors.forename: I
authors.initials: I
authors.lastname: Zavrski
authors.forename: K
authors.initials: K
authors.lastname: Possinger
mesh_terms: D001773:Blood Cells / Q000473:pathology; D001853:Bone Marrow / Q000473:pathology; D016022:Case-Control Studies; D003937:Diagnosis, Differential; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping; D009101:Multiple Myeloma / Q000175:diagnosis* / Q000473:pathology; D010265:Paraproteinemias / Q000175:diagnosis* / Q000473:pathology; D010950:Plasma Cells / Q000276:immunology* / Q000473:pathology