V. Molecular classification and risk stratification of myeloma

Abstract

Multiple myeloma (MM) cells are the malignant counterpart of post-germinal centre (GC) long-lived plasma cells (PCs), characterized by strong bone marrow (BM) dependence, somatic hypermutation of immunoglobulin (Ig) genes and isotype class-switch resulting in absence of IgM expression in all but 1% of tumours. However, MM cells differ from healthy PCs because they retain the potential for a low rate of proliferation (1–3% of cycling cells). Virtually every case of MM is preceded by a premalignant PC tumour called monoclonal gammopathy of undetermined significance (MGUS) that, like MM, produces a typical M-spike (almost always non-IgM) by serum protein electrophoresis (SPEP) or free light chain in the urine [1].