They may occur as multiple primary tumors or as a recurrence from a previous plasmacytoma. Association with the Epstein–Barr virus
Rarely, the Epstein–Barr virus (EBV) is associated with multiple myeloma and plasmacytomas, 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 plasmacytoma 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 plasmacytoma than multiple myeloma. The tissues involved in EBV+ plasmacytoma 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 plasmacytoma(s) is more likely to progress to multiple myeloma than EBV-negative plasmacytoma(s) suggesting that the virus may play a role in the progression of plasmacytoma to multiple myeloma. Treatment
Radiotherapy is the main choice of treatment for both SPB and extramedullary plasmacytoma, and local control rates of >80% can be achieved. This form of treatment can be used with curative intent because plasmacytoma is a radiosensitive tumor. Surgery is an option for extramedullary plasmacytoma, but for cosmetic reasons it is generally used when the lesion is not present within the head and neck region. Another option is the possible combination of radiotherapy with anti-multiple myeloma treatment.
See also
Plasma cell dyscrasia
Multiple myeloma
Monoclonal gammopathy of undetermined significance (MGUS)
Waldenströms macroglobulinemia
Cutaneous B-cell lymphoma

References
External links
Overview at National Cancer Institute