<B>Myeloma </B>

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Myeloma

Etiology:

• Unknown.

Pathogenesis:

• Clinically, myeloma presents either because of the local effects of tumor, or by the paraprotein synthesis.
• Local effects include bone pain and pathological fractures.
• In addition, the replacement of the marrow by the tumor can result in anemia.
• Reduction in white blood cell formation by the marrow can result in an increase in the frequency and severity of infections.
• The paraprotein may result in hyperviscosity symptoms (lethargy, abnormal bleeding).
• The paraprotein also results in increased turnover of normal serum immunoglobulin, so that antibody mediated defence against infectious agents is impaired.
• The paraprotein effects also include symptoms due to excretion of the protein in the kidney, followed by renal damage due to cast formation in the tubules.
• Amyloid deposition due to the light chains is a frequent complication of multiple myeloma..
• The lytic lesion is believed to be due to activation of osteoclasts by cytokines liberated by the plasma cells. These cytokines include IL-1 and TGF-beta.
• IL6 may be produced primarily by stromal cells, activated by the plasma cells.
• IL6 levels are used to measure progress of the tumor.

Epidemiology:

• The tumor primarily affects individuals in the sixth and seventh decades of life.
• Males and females are approximately equally affected.

General Gross Description:

• Myeloma, also known as multiple myeloma.
• A malignant tumor of plasma cell origin.
• Grossly, myeloma is typified by multiple round deposits in various bones of the body.
• These deposits are typically soft, gelatinous tan-white masses that are sharply demarcated.
• The most freqently affected is the spine, followed by skull, pelvis, lung bones.

General Microscopic Description:

• Microscopically, lesion is characterized by plasma cells, which may look like normal plasma cells, or may show various levels of atypia.

Clinical Correlations:

• Characteristic of multiple myeloma is the presence of an abnormal, monoclonal antibody peak on serum electrophoresis.
• In some instances, the plasma cells do not make complete immunoglobulin molecules. In such cases, the light chains made can be excreted quantitatively in urine as Bence Jones protein.
• X-ray of affected bone shows characteristic sharply defined "punched out" lesions that are purely lytic.
• The prognosis is dismal, with few, if any survivors, at five years.

References:
•Robbins "Pathologic Basis of Disease". (Cotran, Kumar and Robbins, Eds.) 5th Edition. pp 663.