Definition
-
Multiple myeloma is the most common primary malignant tumor of bone.
-
It is a plasma cell disorder characterized by monoclonal proliferation of malignant plasma cells.
-
The disease produces osteolytic bone lesions due to increased osteoclastic activity and suppression of osteoblastic bone formation.
Epidemiology
-
Peak incidence occurs between the fifth and seventh decades of life.
-
There is a male predominance, with a ratio of approximately two to one.
-
Along with metastatic carcinoma, multiple myeloma must be considered in any patient older than forty years presenting with a new bone lesion.
Common Anatomical Sites
-
Spine is the most frequently involved site.
-
Ribs and pelvis are the next most common locations.
-
Other commonly affected bones include:
-
Proximal femur
-
Proximal humerus
-
-
Pathologic fractures are common due to extensive bone destruction.
Clinical Features
-
Bone pain is the most frequent presenting symptom.
-
Pain is often of short duration, reflecting aggressive disease progression.
-
Pathologic fractures occur relatively frequently.
-
Unlike many other primary bone tumors, systemic symptoms are often present at initial presentation.
Systemic Manifestations
-
Generalized weakness and unintentional weight loss.
-
Anemia and thrombocytopenia due to marrow infiltration.
-
Hypercalcemia resulting from increased bone resorption.
-
Renal failure caused by deposition of light chains in renal tubules.
-
Peripheral neuropathy, particularly in osteosclerotic variants.
Radiographic Features
-
Multiple, well-defined “punched-out” lytic lesions.
-
Lesions are purely lytic with sharp margins.
-
Absence of surrounding reactive sclerosis.
-
Most lesions are negative on bone scintigraphy due to lack of osteoblastic activity.
-
Rare variants may demonstrate:
-
Diffuse skeletal sclerosis
-
Ballooning or expansion of bone
-
Laboratory Diagnosis
-
Serum immunoelectrophoresis demonstrates a monoclonal gammopathy.
-
Complete blood count frequently shows:
-
Anemia
-
Thrombocytopenia
-
-
Serum biochemistry may reveal:
-
Hypercalcemia
-
Renal dysfunction
-
Staging Investigations
-
Skeletal survey to determine the extent of bone involvement.
-
Bone marrow biopsy to confirm plasma cell infiltration.
-
Biopsy of a bone lesion is required only when the diagnosis is uncertain.
Histopathology
-
Diffuse replacement of normal marrow by sheets of plasma cells.
-
Tumor cells exhibit:
-
Eccentric nuclei with a characteristic “clock-face” chromatin pattern
-
Abundant cytoplasm
-
Prominent perinuclear clearing (halo)
-
-
Amyloid deposition is common and highly suggestive of myeloma when present in bone.
Solitary Plasmacytoma
-
A localized plasma cell tumor without evidence of systemic disease.
-
Bone marrow biopsy and skeletal survey are normal.
-
Histologic appearance is similar to multiple myeloma.
-
Important differential diagnosis includes chronic osteomyelitis.
Immunohistochemistry
-
Plasmacytoma shows monoclonal kappa or lambda light chain expression.
-
Chronic osteomyelitis demonstrates polyclonal plasma cells.
-
Myeloma cells are typically CD56 positive.
-
Lymphoma cells are positive for CD45 and CD20, aiding differentiation.
Primary Treatment
-
Systemic chemotherapy is the mainstay of treatment.
-
Radiation therapy provides rapid pain relief for symptomatic skeletal lesions.
-
Bisphosphonates reduce skeletal-related events and alleviate bone pain.
Role of the Orthopaedic Surgeon
-
Management of impending or established pathologic fractures.
-
Commonly involved surgical sites include:
-
Spine
-
Acetabulum
-
Proximal femur
-
Proximal humerus
-
-
Primary goal is early mobilization and restoration of full weight bearing.
Surgical Principles
-
Tumor debulking combined with stable internal fixation.
-
Fixation is often augmented with polymethyl methacrylate bone cement.
-
When fixation does not permit immediate weight bearing:
-
Cemented arthroplasty
-
Cemented hemiarthroplasty
are preferred options.
-
Postoperative Care
-
Local radiotherapy is typically initiated two to three weeks after surgery, or after adequate wound healing.
-
Close postoperative surveillance is essential.
Perioperative Risks
-
Increased risk of surgical site infection.
-
Higher incidence of deep vein thrombosis.
-
Risk of perioperative renal failure, particularly in advanced disease.
Prognosis
-
Solitary plasmacytoma has a better prognosis than systemic multiple myeloma.
-
More than fifty percent of solitary plasmacytoma cases eventually progress to multiple myeloma.
-
Some patients remain disease-free for prolonged periods.
-
With modern combination therapy, long-term survival exceeding sixty percent has been reported in selected centers.
Leave a Reply