Serum protein electrophoresis of an individual with polyclonal antibodies (top) and an individual with a large paraprotein (bottom). The diagnosis of<unk>  uses a diverse range of interdisciplinary techniques including serum protein electrophoresis, bone marrow biopsy, urine analysis for Bence Jones protein and complete blood count, plain film radiography, MRI and PET-CT. Serum protein electrophoresis separates the proteins in the liquid part of the blood (serum), allowing the analysis of antibodies. Normal blood serum contains a range of antibodies and are said to be polyclonal, whereas serum from a person with<unk>  may show a monoclonal spike. This is due to an outgrowth of a single type of plasma cell that forms the<unk>  and produces a single type of antibody. The plasma cells are said to be monoclonal and the excessively produced antibody is known as monoclonal protein or paraprotein. Paraproteins are present in 60% of SPB and less than 25% of extramedullary<unk> . Bone marrow biopsies are performed to ensure the disease is localised; and in SPB or extramedullary<unk>  there will not be an increase of monoclonal plasma cells. Tissue biopsies of SPB and extramedullary<unk>  are used to assess the phenotype of the plasma cells. Histological analyses can be performed on these biopsies to see what cluster of differentiation (CD) markers are present and to assess monoclonality of the cells. CD markers can aid in the distinction of extramedullary<unk>  from lymphomas. Skeletal surveys are used to ensure there are no other primary tumors within the axial skeleton. MRI can be used to assess tumor status and may be advantageous in detecting primary tumors that are not detected by plain film radiography. PET-CT may also be beneficial in detecting extramedullary tumours in individuals diagnosed with SPB. CT imaging may be better than plain film radiography for assessing bone damage. An important distinction to be made is that a true<unk>  is present and not a systemic plasma cell disorder, such as multiple myeloma. The difference between<unk>  and multiple myeloma is that<unk>  lacks increased blood calcium, decreased kidney function, too few red blood cells in the bloodstream, and multiple bone lesions (collectively termed CRAB). Classification Micrograph of a<unk> .<unk>  is a tumor of plasma cells. The cells are identical to those seen in multiple myeloma, but they form discrete masses of cells in the skeleton (solitary<unk>  of bone; SPB) or in soft tissues (extramedullary<unk> ; EP). They do not present with systemic disease, which would classify them as another systemic plasma cell disorder. The International Myeloma Working Group (IMWG) has published criteria for the diagnosis of<unk> s. They recognise three distinct entities: SPB, extramedullary<unk>  and multiple solitary<unk> s (+/- recurrent). The proposed criteria for SPB is the presence of a single bone lesion, normal bone marrow (less than 5% plasma cells), small or no paraprotein, no related organ involvement/damage and a normal skeletal survey (other than the single bone lesion). The criteria for extramedullary<unk>  are the same but the tumor is located in soft tissue. No bone lesions should be present. Criteria for multiple solitary<unk> s (+/- recurrent) are the same except either multiple solitary bone or soft tissue lesions must be present. They may occur as multiple primary tumors or as a recurrence from a previous<unk> . Association with the Epstein–Barr virus Rarely, the Epstein–Barr virus (EBV) is associated with multiple myeloma and<unk> s, particularly in individuals who have an immunodeficiency due to e.g. HIV/AIDS, organ transplantation, or a chronic inflammatory condition such as rheumatoid arthritis. EBV-positive multiple myeloma and<unk>  are classified together by the World Health Organization (2016) as Epstein–Barr virus-associated lymphoproliferative diseases and termed Epstein–Barr virus-associated plasma cell myeloma. EBV-positivity is more common in<unk>  than multiple myeloma. The tissues involved in EBV+<unk>  typically show foci of EBV+ cells with the appearance of rapidly proliferating immature or poorly differentiated plasma cells. These cells express products of EBV genes such as EBER1 and EBER2. EBV-positive<unk> (s) is more likely to progress to multiple myeloma than EBV-negative<unk> (s) suggesting that the virus may play a role in the progression of<unk>  to multiple myeloma.
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Ameloblastoma