Multiple Myeloma

Multiple myeloma is a malignant tumor of plasma cells that causes widespread osteolytic bone damage. Multiple myeloma is the most common primary tumor of bone and is found in the spine, skull, ribs, sternum and pelvis but may affect any bone with hematopoietic red marrow. The average patient age is over fifty years old and men are affected twice as often as women.
The presenting symptom of multiple myeloma is usually pain. The patient may have a normocytic, normochromic anemia secondary to marrow failure and an increased ESR. Hypercalcemia may cause confusion, weakness and lethargy. Other symptoms may include cachexia, spinal cord compression and renal insufficiency. Bacterial infections are common because of a lack of normal immunoglobulin production. Monoclonal immunoglobulin is found on serum electrophoresis. Light chain subunits of immunoglobulin are called BenceJones proteins and are present in urine.
The radiological appearance of multiple myeloma is characterized by irregular lytic defects of different sizes. These lytic areas are often described as "punched out" and have no periosteal reaction. Erosion begins intramedullarly and progresses through the cortex. MRI is useful for delineating spinal lesions. Bone scan can fail to have increased uptake in 25% of patients suggesting a plain film skeletal survey should always be done.l
On gross examination, the marrow space has been replaced by a diffuse gelatinous red brown tissue. Tumor nodules of approximately 1 cm in size may be present.
Microscopically, multiple myeloma is composed of sheets of plasma cells. The degree of cytologic atypia of these cells has no prognostic value. The osteolytic lesions are caused by increased osteoclastic resorption that is stimulated by cytokines released by-the plasma cells.
Treatment of multiple myeloma consists of palliative chemotherapy or bone marrow transplant. Only patients with complete remission of their disease experience any bony healing. Bisphosphonates are used to inhibit resorption of bone and subsequent hypercalcemia. Untreated, a patient with bony lesions will only survive an average of 6-12 months. The cause of death is usually infection or a hemorrhage.

l Mankin, Henry, Metabolic Bone Dlsease, Instructional Course Lectures, 44:3-29, 1995.

Bulloughs, Peter, Orthopaedic Patholoev (third edition), Times Mirror International Publishers Limited, London, 1997. Cotran, Robbins and Kumar, Robbins Pathologic Basis for Disease, W.B. Saunders, Co., 1994. Huvos, Andrew, Bone Tumors: DiaXnosis, Treatment and Prognosis, W.B. Saunders, Co., 1991. Wundry, GR and T. Yoneda, Facilitation and suppression of bone metastasis, Clinical Orthopaedics and Related Research, 321:34-44, March,





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