Defined as a discrete, solitary mass of monoclonal plasma cells which are malignant and occur in either bone or soft tissue.

Types include: solitary bone plasmacytoma or soft tissue extramedullary plasmacytoma.

Plasmacytomas mostly arise as direct extension from skeletal tumors when they disrupt cortical bone.

Extra skeletal soft tissue lesions are present in 70% of patients with myeloma at autopsy.

40% of patients with multiple myeloma at autopsy infiltration of the liver.

Can exist with a normal bone marrow or with less than 10% clonal bone marrow plasma cells.

Extra skeletal disease results from metastatic spread with 68-85% of plasmacytomas observed at diagnosis consisting of soft tissue masses adjacent to bone lesions, and the remaining lesions resulting from hematogenous spread.

Most plasmacytomas consist of soft tissue masses arising from focal bone involvement, especially from the vertebrae, ribs, sternum, skull or pelvis.

Hematogenous spread extra medullary lesions may be single or multiple subcutaneous nodules which are highly vascularized with a red purple appearance in this scan or in parenchymal organs such as the liver, kidney, breast, lymph nodes or CNS tissue.

CNS involvement occurs in approximately 1% of patients with multiple myeloma, and is manifested as leptomeningeal disease.

Extra medullary disease of the CNS in MM is associated with poor prognosis with a median survival of three months.

Incidence of extra medullary disease in MM when newly diagnosed ranges from 7-18%, and an additional 6-20% develop plasmacytomas later in the course of their illness.

Up to 45% of patients with extra medullary plasmacytomas at the time of diagnosis develop soft tissue involvement at the time of relapse.

Criteria for diagnosis includes: single area of bone destruction due to monoclonal plasma cells, bone marrow infiltration less than 5% of all nucleated cells, absence of other lytic or soft tissue involvement, absence of anemia, hyperkalemia, or renal impairment, low concentrations of serum or urine monoclonal proteins, if present, ad preserved levels of uninvolved immunoglobulin.

Solitary lesion usually treated with radiation therapy.

Can arise in any part of the body.

Bone lesions arise from plasma cells in the bone marrow, and extramedullary plasmacytoma arises from plasma cells in mucosal surfaces.

Recurrent losses in chromosome 13, chromosome arm 1p and chromosome arm 14q with gains in chromosome arms 19p, 9q, and 1q.

High-frequency soft tissue involvement in IgD myeloma.

Higher frequency of a medullary relapse occurs in patients who have undergone allogeneic transplantation treatment.

Patients undergoing autologous stem cell transplantation have a extra medullary relapse rate of 9-14%.

Extramedullary disease at diagnosis is the only significant predictor of plasmacytoma, recurrence with a relative risk as high as 13 (Varottoni M et al).

IL-6 is the principal growth factor in progression of this disorder and other plasma cell disorders.

High grade angiogenesis in solitary plasmacytoma associated with increased progression to myeloma and with a shorter progression free survival.

Treatment is to administer adequate doses of radiation therapy of at least 40-50 Gy to the involvef field with or without surgery.

Chemotherapy not utilized until evidence of multiple myeloma is present.

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