Table 1.

Definitions of plasma cell neoplasms.

Plasma cell neoplasm	Definition
Extramedullary disease	An aggressive form of multiple myeloma characterized by the presence of soft-tissue plasmacytomas that result from hematogenous spread
Paraskeletal plasmacytoma	A form of multiple myeloma characterized by the presence of soft-tissue plasmacytomas that occur due to direct growth from skeletal tumors following cortical bone disruption
Solitary plasmacytoma	A single mass of clonal plasma cells (bone or extramedullary) with no or minimal BM plasmacytosis and with no other symptoms than those derived from the primary lesion
Plasma cell leukemia	A rare and aggressive variant of myeloma characterized by the presence of circulating plasma cells; diagnosis is based upon the percentage (≥20%) and absolute number (≥2 × 109/L) of plasma cells in peripheral blood