Diagnostic Steps for a Lytic Bone Lesion
The diagnostic workup for a lytic bone lesion should begin with whole-body low-dose computed tomography (WBLD-CT), which is the current standard procedure for detecting lytic lesions due to its superior sensitivity compared to conventional radiography. 1
Initial Imaging
- WBLD-CT is recommended as the first-line imaging technique for detecting lytic bone lesions, as it provides high-resolution images of cortical and trabecular bone and can detect small lesions (<5mm) 1
- If WBLD-CT is not available, conventional radiography (skeletal survey) can be used, though it is less sensitive and only detects lesions when more than 30% of cortical bone is destroyed 1
- In lytic lesions with suspected plasmacytoma or multiple myeloma, WBLD-CT shows a characteristic mixed, predominantly lytic pattern, with the trabecular bone replaced while cortical bone is partly conserved 1
Advanced Imaging
- Magnetic Resonance Imaging (MRI) should be performed if no lytic lesions are found on WBLD-CT but clinical suspicion remains high 1
- MRI is particularly valuable for detecting bone marrow involvement and soft tissue extension, appearing as infiltration with low T1 and high T2 signal intensity 1
- Positron Emission Tomography/CT (PET/CT) should be considered when evaluating metabolically active lesions and may detect additional lesions missed by other imaging modalities 1
- In cases of suspected spinal cord compression, MRI is the gold standard, though CT can be used if MRI is unavailable 1
Tissue Sampling
- Biopsy is essential for definitive diagnosis of lytic bone lesions, as they can result from various etiologies including malignant, benign, and infectious processes 2, 3
- CT-guided percutaneous bone biopsy of lytic lesions has excellent diagnostic yield (reported as high as 100% in some studies) with a very low complication rate (2%) 4
- Ultrasound-guided fine-needle aspiration biopsy may be useful for lesions that can be clearly visualized with ultrasound, particularly in the thoracic skeleton and pelvic bone 5
Laboratory Evaluation
- For suspected multiple myeloma or plasmacytoma:
- Bone marrow aspiration and biopsy should be performed to evaluate plasma cell morphology and degree of infiltration 1
- Serum protein electrophoresis, urine protein electrophoresis, and quantification of immunoglobulins (IgG, IgA, IgM) should be performed 1
- Characterization of heavy and light chains by immunofixation is recommended 1
- Serum-free light-chain measurement is important for identifying and monitoring nonsecretory multiple myeloma 1
Differential Diagnosis
- Common causes of lytic bone lesions include:
Pitfalls and Caveats
- Conventional radiography may miss early lytic lesions and extramedullary plasmacytomas in soft tissues, leading to underdiagnosis 1
- When evaluating for multiple myeloma, finding a solitary lesion on plain radiographs does not rule out additional lesions that may be detected with more sensitive imaging techniques 1
- For bone biopsies requiring decalcification, special attention should be paid to the processing method as traditional decalcification can damage nucleic acids, potentially interfering with molecular testing 4
- Tuberculosis can cause primary lytic bone lesions that mimic malignancy, so mycobacterial cultures should be included when analyzing biopsies of lytic bone lesions 3
Follow-up Imaging
- For patients with confirmed multiple myeloma or plasmacytoma, follow-up imaging should be performed to monitor response to treatment 1
- PET/CT may be particularly useful for defining complete response and monitoring disease progression 1
- Healing of lytic lesions is slow, taking 3-6 months to begin appearing and more than a year to mature 6