CSP: rare type of acute leukemia in which the predominating cell in the peripheral blood is the plasma cell; it is often seen in conjunction with multiple myeloma and may be a variant form of that disease.,MSH: A rare, aggressive variant of MULTIPLE MYELOMA characterized by the circulation of excessive PLASMA CELLS in the peripheral blood. It can be a primary manifestation of multiple myeloma or develop as a terminal complication during the disease.,NCI: An aggressive plasma cell neoplasm with usually short survival. It is characterized by the presence of neoplastic plasma cells in the peripheral blood. The peripheral blood plasma cells comprise more than 20% of the peripheral blood white cells. It may be the initial presentation of a plasma cell neoplasm or manifest as a terminal complication of plasma cell myeloma. Lymphadenopathy and organomegaly are frequent clinical signs, whereas bone pain and osteolytic lesions are less frequently present.