ABSTRACT
Plasma cell myeloma (PCM) is a clonal late B-cell disorder in which malignant plasma cells expand and accumulate in the bone marrow (BM) resulting in cytopenias, bone resorption, and production of serum monoclonal protein (M-protein). Minor subset of patients with PCM has true nonsecretory disease and has no evidence of an M-protein in the serum. The diagnostic criteria for symptomatic PCM are as follows: M-protein in serum or urineBM clonal plasma cells or plasmacytomaRelated organ or tissue impairment. The diagnostic criteria for asymptomatic PCM are as follows: M-protein in serum at myeloma levels and/or=10% clonal plasma cells in the BMNo related organ or tissue impairment. Asymptomatic PCM is similar to monoclonal gammopathy of undetermined significance in its lack of clinical manifestations, but is much more likely to progress to symptomatic myeloma. In early PCM or posttreatment lesions, plasma cells may be difficult to identify and distinguish from reactive plasmacytosis. Immunohistochemistry helps in visualizing plasma cells and confirming their clonality.
