Distribution of Sclerotic Lesions in Multiple Myeloma
Sclerotic lesions in multiple myeloma are extremely rare, occurring in only 3% of cases, and when present, they can appear as isolated sclerotic deposits, mixed lytic-sclerotic lesions, or rarely as diffuse osteosclerosis affecting multiple skeletal sites. 1, 2
Typical Skeletal Distribution
The most common skeletal sites affected by multiple myeloma (whether lytic or sclerotic) include:
- Pelvis, skull, spine, ribs, and the shafts of the femur and humerus are the classic locations 1
- The spine is frequently involved, with sclerotic lesions potentially affecting any vertebral level 3, 4
- Uncommon sites such as the orbit have been documented in sclerotic variants 2
- Chest wall involvement with expansile thick spiculated sclerosis in ribs has been reported 2
Patterns of Sclerotic Presentation
Sclerotic myeloma manifests in three distinct radiographic patterns:
- Isolated sclerotic deposits: Single focal areas of bone sclerosis 4, 2
- Mixed lytic-sclerotic lesions: Combination of both destructive and sclerotic changes, seen in two-thirds of solitary plasmacytoma cases 3, 2
- Diffuse osteosclerosis: Widespread sclerotic involvement throughout the skeleton, which is extremely rare 5, 4
Association with POEMS Syndrome
Sclerotic lesions in multiple myeloma are frequently associated with POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M protein, skin changes). 6, 4
- Multiple scattered skeletal lesions with sclerotic margins are characteristic of POEMS-associated myeloma 2
- Sclerotic lesions may appear as spiculated or hair-on-end patterns on radiographs 1, 2
- However, diffuse osteosclerosis can occur without other POEMS criteria 4
Critical Diagnostic Considerations
Plain radiographs are inadequate for detecting early myeloma lesions, as they only identify lytic lesions when >30% of cortical bone is destroyed. 3
- MRI with gadolinium contrast is the gold standard for evaluating vertebral abnormalities and bone marrow involvement 3
- CT scanning provides superior cortical bone detail and can identify small lytic areas within sclerotic lesions missed on plain films 3
- Whole-body imaging (CT or bone scan) is essential to determine if lesions are solitary or part of systemic disease 3
Mandatory Workup for Sclerotic Vertebral Lesions
When encountering sclerotic lesions suspicious for myeloma:
- Serum protein electrophoresis and immunofixation must be performed to exclude plasma cell dyscrasia 3
- Unilateral bone marrow aspiration and trephine biopsy with immunophenotyping to detect monoclonal plasma cells (>10% confirms multiple myeloma) 3
- Flow cytometry or kappa/lambda labeling to determine clonal plasma cell percentage 3
Key Clinical Pitfalls
The presence of bone sclerosis does not exclude multiple myeloma—although exceptional, myeloma must be considered in any pattern of bone sclerosis. 4
- Relying solely on the classic lytic presentation will miss the 3% of cases with primary sclerotic manifestations 1, 2
- Missing soft tissue masses that may cause spinal cord compression, which requires urgent MRI evaluation 3, 4
- Assuming sclerotic lesions represent benign processes such as osteoarthritis or healed fractures without proper workup 3