Plasma Cell Leukemia

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Image Description

Plasma Cell Leukemia (PCL) is an aggressive form of myeloma in which the neoplastic plasma cells make up more than 20% of leukocytes in the peripheral blood. PCL may be present at the time of initial diagnosis (primary) or evolve later in an established case of myeloma (secondary). About 60% of PCL cases are primary and they account for 2% to 5% of myelomas.

PCL vs Myeloma: When compared to multiple myeloma, the patients with PCL tend to be younger and more commonly have lymphadenopathy, organomegaly, renal complications, anemia and thrombocytopenia. On the other hand, lytic bone lesions and bone pain are less common. PCL is often CD56 negative in contrast to myeloma. PCL tends to be associated more frequently with IgD, IgE, and light-chain only myelomas in contrast to IgG or IgA myelomas. Abnormal karyotype and unfavorable cytogenetics are more frequently associated with PCL.

PCL is a highly aggressive neoplasm with dismal prognosis. It does not respond well to therapy and the median survival is much shorter than with typical myelomas.

The image shows a peripheral blood smear from a case of plasma cell leukemia. There are four proplasmacytes (black arrows) with dispersed nuclear chromatin and prominent nucleoli. Rouleaux of red cells is present in the background. Wright-Giemsa stain. 100X oil. Courtesy of: Jian-Hua Qiao, MD, FCAP, Los Angeles, CA, USA.

About the Disease

Plasma cell disorders are B-cell neoplasms composed of plasma cells or lymphocytes that secrete a monoclonal immunoglobulin (Ig) or Ig fragment. They are responsible for about 15% of deaths caused by lymphoid malignancies in the US. The monoclonal Ig, usually identified by serum or urine protein electrophoresis, is known as the M component. Sometimes the M component consists of only light chains or heavy chains. Free light chains are referred to as Bence-Jones proteins when they are excreted in urine. The WHO Classification (2008) of plasma cell neoplasms includes the following: Monoclonal Gammopathy of Undetermined Significance (MGUS): MGUS refers to an asymptomatic patient with an M component (<3 gm/dl) in their blood. It is the most common plasma cell disorder and is seen in about 5% of individuals >70 years of age. About 1% of MGUS patients per year develop multiple myeloma, amyloidosis, macroglobulinemia, or other lymphoproliferative disorder. The median interval between the diagnosis of MGUS and the development of malignancy is about 10.5 years. Plasma Cell Myeloma: Multiple myeloma (MM) is a plasma cell neoplasm of older individuals that is characterized by scattered tumorous masses causing lytic bone lesions in the axial skeleton, hypercalcemia, renal damage, and acquired immune abnormalities. Solitary Plasmacytoma: About 3% to 5% of patients with plasma cell disorders present with solitary bone or soft tissue mass. An M component may be found in serum or urine in a small percentage of cases. Solitary bone plasmacytoma slowly progresses to multiple myeloma in most cases. Extraosseous plasmacytomas involve lungs, nasopharynx, oropharynx, or nasal sinuses and can often be cured by resection. Immunoglobulin Deposition Diseases: This group includes primary amyloidosis (PA) and light- or heavy- chain deposition disease. Immunoglobulins are deposited in various tissues eventually leading to organ failure. About 20% of PA patients have multiple myeloma (MM). The remainder don't meet the criteria for MM but have a small M component and increased plasma cells in bone marrow. Osteosclerotic Myeloma (POEMS Syndrome): Osteosclerotic myeloma is usually associated with polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin lesions (POEMS syndrome). Some patients also develop Castleman's disease, serous effusions, and thrombocytosis.

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