What is the appropriate workup for a solitary lytic lesion in the wrist of a middle‑aged or older adult when multiple myeloma is suspected?

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Workup for Lytic Wrist Lesion with Suspected Multiple Myeloma

When a lytic lesion in the wrist raises suspicion for multiple myeloma, immediately obtain whole-body low-dose CT or FDG-PET/CT (not just plain radiographs), perform comprehensive serum and urine protein studies, and proceed with unilateral bone marrow aspiration and biopsy with flow cytometry to establish the diagnosis. 1

Advanced Imaging: First Critical Step

Whole-body low-dose CT or FDG-PET/CT is now the standard imaging modality, replacing conventional skeletal surveys for initial diagnostic workup. 1 The NCCN 2020 guidelines explicitly recommend these advanced imaging techniques because:

  • Whole-body CT detects 25.5% more lesions in patients with negative skeletal surveys, particularly in the spine and pelvis 1
  • Skeletal surveys miss lesions until >30% of cortical bone is destroyed 1
  • If PET/CT is chosen, ensure the CT component has diagnostic quality equivalent to whole-body low-dose CT, not just attenuation correction 1
  • Skeletal survey is only acceptable when advanced imaging is unavailable 1

MRI of the spine and pelvis should be added if solitary plasmacytoma is suspected, as it is mandatory to exclude additional occult lesions that would change the diagnosis to multiple myeloma. 1

Complete Laboratory Workup

The International Myeloma Workshop consensus panel specifies these essential tests 1:

Protein Studies (Mandatory)

  • Serum protein electrophoresis (SPEP) with immunofixation 1, 2
  • Serum free light chain (FLC) assay - critical for detecting light chain disease 1
  • Quantitative immunoglobulins (IgG, IgA, IgM) 1
  • 24-hour urine collection with urine protein electrophoresis (UPEP) and immunofixation 1

Additional Required Labs

  • Complete blood count (assess for anemia) 1, 3
  • Serum creatinine (renal function) 1, 3
  • Serum calcium (hypercalcemia is a CRAB criterion) 1, 3
  • Serum β2-microglobulin - required for International Staging System 1
  • Serum lactate dehydrogenase (LDH) - independent prognostic significance 1
  • Serum albumin 1

Bone Marrow Evaluation: Definitive Diagnostic Step

Unilateral bone marrow aspiration AND trephine biopsy are both required for all patients with suspected solitary plasmacytoma or multiple myeloma. 1

Critical Technical Requirements

  • Perform both aspiration and biopsy during the same procedure - biopsy provides more reliable assessment of plasma cell infiltration and prevents need for repeat procedures 1
  • Flow cytometry on the bone marrow aspirate is essential to determine the proportion of clonal plasma cells using kappa/lambda labeling 1
  • If flow cytometry unavailable, use immunohistochemistry on the biopsy specimen 1
  • Record the highest plasma cell percentage from either aspiration or biopsy when results differ 1

Diagnostic Thresholds

  • >10% clonal plasma cells = multiple myeloma diagnosis (excludes solitary plasmacytoma) 1
  • Flow cytometry positivity predicts progression: 71% of flow-positive patients progress to MM versus only 8% of flow-negative patients 1

Cytogenetic Studies (Prognostic)

Standard metaphase cytogenetics AND FISH analysis should be performed at initial assessment 1:

  • FISH probes must include: del(17p), t(4;14), t(14;16) 1
  • These identify high-risk disease that affects treatment decisions 4, 5
  • Despite low yield (20%), metaphase cytogenetics captures uncommon abnormalities 1

Distinguishing Solitary Plasmacytoma from Multiple Myeloma

This distinction is critical because it completely changes prognosis and treatment:

Solitary plasmacytoma requires 1:

  • Single bone or extramedullary lesion
  • <10% clonal plasma cells in bone marrow
  • No other lytic lesions on whole-body imaging
  • No CRAB features (hypercalcemia, renal failure, anemia, bone lesions) attributable to plasma cell disorder

Multiple myeloma is diagnosed when 4, 6, 5:

  • ≥10% clonal bone marrow plasma cells OR biopsy-proven plasmacytoma PLUS
  • At least one myeloma-defining event: CRAB features, ≥60% bone marrow plasma cells, serum FLC ratio ≥100 (with involved FLC ≥100 mg/L), or >1 focal lesion on MRI

Common Pitfalls to Avoid

  • Do not rely on plain radiographs alone - they miss 25-30% of lesions detected by advanced imaging 1
  • Do not skip bone marrow biopsy even if aspiration is adequate - biopsy may reveal higher plasma cell infiltration due to sampling error 1
  • Do not omit flow cytometry - it identifies occult clonal disease in 49% of apparent solitary plasmacytoma cases and predicts progression risk 1
  • Do not forget spine/pelvis MRI when solitary plasmacytoma is suspected - additional lesions would change diagnosis to MM 1
  • Do not order ESR - it provides no additional diagnostic or prognostic information 1

Algorithmic Summary

  1. Imaging: Whole-body low-dose CT or FDG-PET/CT + MRI spine/pelvis 1
  2. Labs: SPEP/UPEP with immunofixation, serum FLC, quantitative Ig, CBC, creatinine, calcium, β2-microglobulin, LDH, albumin 1
  3. Bone marrow: Aspiration + biopsy with flow cytometry and cytogenetics/FISH 1
  4. Diagnosis: Apply IMWG criteria to distinguish solitary plasmacytoma from multiple myeloma 4, 6, 5

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

3
Research

Multiple Myeloma: Diagnosis and Treatment.

American family physician, 2017

6
Research

Multiple myeloma.

Nature reviews. Disease primers, 2024

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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