Organ Systems, Bone Marrow, Multiple Myeloma, WHO Classification, Hematopathology

Smoldering (Asymptomatic) Myeloma 

Smoldering (Asymptomatic) Myeloma 
  • >3 gm/dL serum M protein (or) urinary M protein ≥500 mg/24 hours
  • (and/or) 10-60% bone marrow plasma cells (usually 10-20% plasma cells)
  • Asymptomatic patients with no evidence of end-organ damage or biomarker evidence of malignancy (myeloma-defining events)

  • 75% will progress to multiple myeloma over 15-years
    • 10%/year – first 5 years
    • 3%/year – second 5 years
    • 1%/year – after 10 years
Smoldering myeloma is similar to plasma cell myeloma accept there is no evidence of end organ damage.  In this way it is similar to MGUS, but is more likely to progress (higher levels of bone marrow plasma cells and M protein component).
 
 
Myeloma defining events
  • End-organ damage
    • Hypercalcemia (>1 mg/dL above upper limit of normal or >11 mg/dL)
    • Renal insufficiency 
      • Creatinine clearance <40 mL/minute (or)
      • Serum creatinine > 2 mg/dL
    • Anemia
      • Hgb >2 g/dL below lower limit of normal
      • Hgb <10 g/dL
    • Bone lesion(s) – ≥1 lytic lesion (skeletal survey, CT, or CT/PET)
  • Biomarker of Malignancy
    • ≥60% monoclonal plasma cells
    • ≥100 serum free light chain ratio (involved-to-uninvolved)
    • >1 focal lesion on MRI
References
Robbins and Cotran Pathologic Basis of Disease.  V Kumar, et al. 9th Edition. Elsevier Saunders. 2015. pp. 599-601.
 
WHO Classification of Tumors of Haematopoietic and Lymphoid Tissues.  SH Swerdlow, et al. International Agency for Research on Cancer. Lyon, 2008.  pp. 200-213
 
Swerdlow SH, Campo E, Pileri SA, Harris NL, Stein H, Siebert R, et al. The 2016 revision of the World Health Organization classification of lymphoid neoplasms. Blood. 2016;127: 2375–2390. doi:10.1182/blood-2016-01-643569