Role of flow cytometry in plasma cell neoplasms

Plasma cell neoplasms (PCN) are a heterogeneous group of disorders with a spectrum of clinical presentations from asymptomatic monoclonal gammopathy of undetermined significance (MGUS) to smoldering multiple myeloma to symptomatic multiple myeloma (MM). Other less common categories of PCN include AL amyloidosis, POEMS syndrome, and plasma cell leukemia. Typically, the gold standard for diagnosis has been to correlate morphologic assessment with clinical information (hypercalcemia, renal failure, anemia, and lytic bone lesions) and serologic data, including protein and urine electrophoresis with immunofixation, along with serum-free light chain assay data. As technology has improved, especially monoclonal antibody production and instrumentation, multicolor flow cytometry has become an important tool to demonstrate that the plasma cells present in a bone marrow/tissue/fluid specimen are clonal or immunophenotypically abnormal.