Multiple myeloma

Multiple myeloma
Updated: 09/04/2024
© Jun Wang, MD, PhD

General features
  • Plasma cell neoplasm
  • Clinical variants
Asymptomatic (smoldering) myeloma: NO related organ or tissue impairment
Non-secretory myeloma: NO M-protein by electrophoresis or immunofixation; clinical features similar to secretory myeloma except for low incidence of renal insufficiency and hypercalcemia
Plasma cell leukemia: Clonal plasma cells > 20% of the leukocyte differential count; aggressive disease
Clinical presentations
Key pathogenesis
  • DKK1 and FRP2: Inhibit Wnt, blocking bone formation
  • Elevated RANKL, promotes osteoclasts activity, similar to giant cell tumor of bone
  • Suppressed OPG
Key Laboratory findings
  • Monoclonal gammopathy (M spikes)
  • M proteins in serum or urine (Most common IgG, followed by IgA)
  • Bence Jones proteins in urine
  • Elevated immunoglobulin: > 3g/dl (IgG) or >2.5g/dl (IgA)
  • Rouleaux formation
  • Hypercalcemia
  • Abnormal renal functions
Key morphological features
  • Plasma cell infiltrate of marrow or other tissue
  • Abnormal plasma cells: Perinueclear clearing
  • Mott cells: Plasma cells with grapelike cytoplasmic inclusions (Russell bodies)
  • Russell bodies: Cytoplasmic cherry red refractive round bodies
  • Dutcher bodies: Intranuclear crystalline rods
 Markers
  • Positive: CD38, CD138, light chain restriction
  • Negative: CD19, CD20
Diagnostic criteria
  • A bone marrow aspirate or biopsy showing that at least 10 percent of the cells are plasma cells or the presence of a plasma cell tumor (called a plasmacytoma)
  • Plus at least one of the following two features:
Evidence of damage to the body as a result of the plasma cell growth, such as severe bone damage, kidney failure, anemia, or high calcium in the blood, and/or
Detection of one of the following findings: ≥60% plasma cells in the bone marrow; free light chain ratio of 100 or more (provided involved FLC level is at least 100 mg/L); or MRI showing more than one lesion (involving bone or bone marrow)
Genetic abnormalities
  • Various
  • IgH translocations
  • Myc, p53, RAS, RB1, etc
Negative prognosis indicator
  • Elevated IL-6: Promotes tumor cell survival
  • Hypercalcemia
  • Bence Jones proteinemia
  • Renal impairment
  • Translocation t(14;16), t(14;20), t(4;14) and deletion chromosome 17p (p53)

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Contents

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