Utility of flow cytometry immunophenotyping in multiple myeloma and other clonal plasma cell‐related disorders

Six color flow cytometry detects plasma cells expressing aberrant immunophenotype in bone marrow of healthy donors

“…Our findings suggest that ''aberrant'' immunophenotype is normal in a considerable proportion of BM PCs of healthy people. Different authors found that CD19 negative BM PCs could constitute up to 30-39% of the total BM PCs in healthy people (3,(7)(8)(9). Importantly, we showed that the majority of plasmacytes were CD19 negative in some HDs.…”

“…10-25% may express CD56 antigen (3,(7)(8)(9). Heterogeneous expression of CD19 and CD56 could lead to partial immunophenotypic overlap of malignant and normal aberrant (CD19À/CD56þ) BM PCs.…”

Competition between clonal plasma cells and normal cells for potentially overlapping bone marrow niches is associated with a progressively altered cellular distribution in MGUS vs myeloma

“…5,6 Despite the different tumor mass [7][8][9][10][11][12][13][14] and clinical behavior of the disease, clonal PC from MGUS, SMM and MM patients show highly similar and largely overlapping genetic profiles. [15][16][17] In addition, no clear phenotypic differences have been reported so far among clonal PC from MGUS, SMM and MM, 18 except for a few molecules involved in the interaction between PC and their microenvironment. 19 We have previously shown that the proportion of normal PC within the bone marrow (BM) PC compartment (normal PC/BM PC) is an efficient single parameter for discrimination between MGUS and MM; 20 at diagnosis, most MGUS cases (480%) display 45% normal PC/BM PC, 21 whereas the great majority (485%) of symptomatic MM show o5% normal PC/BM PC.…”

Issue Highlights—January 2013

“…MULTIPLE MYELOMA PATIENTS There is accumulating evidence in the literature indicating that multicolor flow cytometry is increasingly important for the diagnosis of minimal residual disease (MRD) assessment of patients with multiple myeloma (MM), although only sporadic reports have proposed consensus techniques for their detection (9)(10)(11)(12). However, the literature contains discrepancies in results regarding the exact immunophenotype of normal and neoplastic plasma cells (PCs) and their associated clinical significance.…”

“…Recent reports have also showed that the immunophenotype of MM PCs can change over time and that normal PCs are heterogeneous in the expression of several immunophenotypic markers such as CD19 and CD56. This implies that for the sensitive, reliable detection of MRD clonality assessment by the detection of cytoplasmic kappa and lambda light chains is advisable (10). In this regard, the data published in this issue of Cytometry by van Velzen et al (13) provide evidence that the use of polyclonal over monoclonal antibodies is preferred for the detection of intracellular immunoglobulin light chains, thus indicating that the recognition of the monoclonal nature of a given cell proliferation may be a difficult task in selected cases of MM and/or related disorders.…”