Plasmacytoma

Excerpt

Plasmacytoma is a rare plasma cell dyscrasia that grows within the axial skeleton or soft tissue structures as solitary or multiple masses without evidence of systemic disease. It is an early plasma cell malignancy and is considered an intermediate phase between monoclonal gammopathy of undetermined significance(MGUS) and multiple myeloma (MM). Plasmacytoma can be divided into the following types according to the International Myeloma Working Group:

Solitary Plasmacytoma

It is further divided into:

1. Solitary plasmacytoma of bone (SPB), which arises from plasma cells of the bone marrow.

2. Extramedullary plasmacytoma (EMP), which arises from plasma cells of the mucosal surfaces.

Multiple Solitary Plasmacytomas (MSP)

Solitary plasmacytoma is the most common form of plasmacytoma. Most cases of plasmacytomas cause paraproteinemia. Metastatic spread of plasmacytoma occurs to soft tissues frequently and occasionally to bones. Plasmacytoma is treated with surgery, radiotherapy, and chemotherapy as required. Therapy for local disease gives prolonged survival, and disseminated disease treatment gives longer remission.

According to the World Health Organization (WHO) update, SPB is further composed of two subtypes:

1. SPB with minimal bone marrow involvement:SPB type that has less than 10% clonal marrow cells apart from the plasmacytoma itself. The rate of progression of this type of SPB to MM is 20-60% in 3 years.

2. SPB with no bone marrow involvement: SPB type that lacks clonal marrow cells apart from the plasmacytoma. The rate of progression of this type to MM is 10% in 3 years.

MSP consists of monoclonal cell infiltrates in one or more lytic bone lesions or extramedullary tissue. Only a few cases of MSP have been reported. Imaging modalities used for solitary plasmacytoma may reveal the presence of multiple lesions leading to MSP diagnosis. MSP is diagnosed in up to 5% of cases of solitary plasmacytoma. Long term prognosis of MSP is not clear. Surgery, radiotherapy, chemotherapy, and stem cell transplantation are indicated for the treatment of MSP.